p.1 

OAR Box 1135 

Prepped by Candice Davis 

Document Number: 

15) M-A-1 

Docket Number: 

A-86-03 

Printed 4/21/200811:41:17 AM Sheet 15 of 65 
.fr-Vi-ca-l.-A-l 

,Energy and Resource Consultants, Inc. 

P.2 

DIESEL FUEL QUALITY EFFECTS ON EMISSIONS, DURABILITY, AND PERFORMANCE 

A report to: 

The U.S. Environmental Protection Agency 

Office of Policy Analysis 

Washington, D.C. 

Draft final report 

EPA Contract //68-01-6543 

Work Assignment No. 50 

by: 

Craig Miller 

Christopher Weaver 

Energy and Resource Consultants, Inc. 

PO Drawer 0 

Boulder, Co. 80306 

and 

William Johnson 

Terrence Higgins 

Sobotka Consultants, Inc. 

2501 M Street N.W. Suite 500 

Washington, D.C. 20037 

September 30, 1985 
P.3 

EXECUTIVE SOrMARY 

Diesel engines in light and heavy-duty vehicles emit significant 

amounts of oxides of nitrogen (NOx), particulate matter, sulfur 

oxides, and unburned hydrocarbons. Etaissions levels for these 

pollutants are strongly affected by the quality and composition 

of the diesel fuel used. This study briefly reviews the 

available data and examines the feasibility, costs, and 

cost-effectiveness of reducing diesel emissions by mandatory 

changes in diesel fuel conposition. Two types of changes are 

considered: (1) a drastic reduction in diesel fuel sulfur 

content, alone or in ccotination with a moderate reduction in the 

fraction of aromatic hydrocarbons in the fuel and (2) effects on 

engine durability, fuel economy, and refining costs. 

The work reported here is intended as a preliminary evaluation of 

the feasibility and cost-effectiveness of diesel emissions 

control through fuel modifications, lhe purpose of this 

preliminary study is to identify the major issues and to roughly 

quantify the costs and benefits of some potential fuel 

modifications in order to determine whether this approach shows 

sufficient premise to warrant further regulatory attention by 

EFA. 

A__EBL_t____i 

A thorough review of the technical literature and other available 

information on fuel-quality effects on emissions was undertaken. 

On the basis of thia review, two scenarios for fuel quality 

ii 
P.4 

improvement were defined. The first scenario included reducing 

diesel fuel sulfur content to O.OS percent by weight, with an 

accompanying" decrease in aromatics. The second scenario included 

a further decrease in aromatic content. A linear-program model 

of the refining industry was used to model the effects of these 

two scenarios coapared with a baseline case. The results of the 

modeling effort were combined with information on maintenance 

costs and savings and emissions reductions due to the improved 

fuel quality to estimate the overall costs and cost-effectiveness 

of each scenario. 

CTm„BTfWt 

The major conclusions of the study are the following. First, the 

most important emissions-related properties of diesel fuel are 

the sulfur content and the fraction of aromatic hydrocarbons. 

Reducing fuel sulfur would reduce SO emissions and the sulfate 

2 

fraction of diesel particulates,, and would indirectly reduce 

ambient levels of sulfate particles. Reducing fuel aromatic 

content would reduce the carbonaceous fraction of diesel 

particulate emissions. Contrary to cannon belief, changes in the 

distillation teaperatures (such as the 90 percent point and end 

point) have little potential for emissions control. 

Second, the sulfur content of automotive diesel fuel could be 

reduced from the present average of about 0.274 percent to 0.048 

percent, without reducing the availability of diesel fuel, and 

using only the present capital stock. This would require 

iii 
P.5 

segregating production of diesel fuel from that of distillate 

burner fuels, as well as high rates of utilization of existing 

desulfurization capacity. The increase in average refining cost 

due to desulfurization would be about 1.2 cents per gallon. The 

average aromatic content of the fuel would also be reduced by 

desulfurization from the present 28.7 percent to about 20.3 

percent by volume. 

Third, reducing the sulfur content of diesel fuel would 

significantly reduce corrosive wear and deposit formation, 

extending engine life and reducing maintenance costs. A 

conservative estimate based on the limited data available 

indicates that these savings would be about four times the 

increase in refining costs. Lowering the sulfur content would 

thus result in significant net savings to society even ignoring 

the environmental benefits. The lower aromatic content due to 

desulfurization would also improve cetane numbers and ignition 

quality, reducing cold starting problems and noise. 

Finally, it would be feasible to reduce aromatic content to 17 

percent by volume using the present capital stock. This would 

increase refining costs by about 0.4 cents per gallon beyond the 

cost of desulfurization. The incremental cost of particulate 

control by this means would be about $5.50 to $10.00 per pound of 

particulate matter eliminated. 

iv 
P.6 

TABLE OF CONTENTS 

EXEOTnVE SOMARY ii 

PREFACE x 

#30m_EIX£MENTS xi i 

1.0 INTRODUCTION 1-1 

1.1 __A_XG_a_ND INKFMATION 1-1 

1.2 OUTLINE OF THE APHCMO. 1-3 

1.3 MAJOR OaCXJUSIOMS OF THE STUDY 1-6 

1.4 LIMITATIONS fiND CAVEATS 1-7 

2 . 0 DIESEL FUEL QUALITY AND COrlPOSITION 2-1 

2 . 1 OCMPOSITION A © PROPERTIES OF A_7IO>CTIVE DIESEL FUEL 2-1 

2.2 DIESEL FUEL QUALITY INDICES 2-6 

2 . 3 OH-ENT FUEL QUALITY STANDARDS AM) I-EOILATIONS 2-11 

2 . 4 TRENDS IN DIESEL FUEL QUALITY 2-13 

3 . 0 FUEL QUALITY EFFECTS ON DIESEL ENGINES 3-1 

3 . 1 FUEL SULFUR OQNTONT 3-2 

3 . 2 AROMATIC OCNTENT AND ICN_TION QUALITY 3-15 

3 . 3 FUEL BOILING RANGE AM) VOLATILITY 3-29 

3.4 EBBITY AND VISCOSITY 3-34 

3 . 5 STABILITY, E__F06IT FCRMATION AM) OTHER FRDPERTIES 3-36 

4 . 0 MXELING THE COSTS OF REFINING CHANGES 4-1 

4 . 1 REFINHtY MCEEL 4-1 

4.2 MCCELING APPROACH 4-4 
P.7 

4.3 MXEL ASSUVPTIONS 4-5 

4.4 MCCEL AND DATA LIMITATIONS 4-13 

5.0 MXEL RESULTS AM) CC6T-I-FFBCTIVENESS fl(ALYSIS 5-1 

5.1 : EEFINITION OF THE TWO SCENARIOS 5-1 

5.2: RESULTS FROMTHE REFINING COST MXEL 5-4 

5.3: SCENARIO ONE: I2ESULFURIZATTON LlrHJUrS ON ENGINES AM) EMISSIONS . 5-12 

5.4: SCENARIO TVO: EEARCMATIZATiaN EFFECTS ON ENGINES AND EMISSIONS . 5-16 

5.5: COOT--__TBCTI VENESS CF FUEL QUALITY REGULATIONS 5-17 

6.0 CONCLUSIONS AND REOOrt'teNDATIONS 6-1 

BIBLICXBAPHY BIB-1 

v i 
P.8 

LIST OF FIGURES 

2.1 Classes of hydrocarbon molecules found in diesel fuel 2-4 

2.2 Relationship between aromatic content and cetane nixnber 2-8 

2.3 Trends in seme properties of type T-T and grade 2-D 2-15 

diesel fuel oils 

2.4 Distribution of diesel fuel aromatic content frcm the 2-17 

MVMA sunnier surveys 

2.5 Distribution of API gravity of diesel fuels from the MVMA 2-18 

surrmer surveys 

2.6 Distribution of calculated cetane index of diesel fuels 2-19 

from the MVMA sunnier surveys 

2.7 Distribution of 90 percent point of diesel fuels frcm the 2-20 

MVMA suomer surveys 

2.8 Distribution of sulfur content of diesel fuels from the MVMA 2-21 

surrmer surveys 

3.1 Effect of fuel sulfur content and oil alkalinity on 3-9 

piston ring wear rates in a locomotive engine 

3.2 Loss of alkalinity in oil during use due to neutralization 3-11 

by sulfur 

3.3 Effect of fuel sulfur content on piston ring wear rate 3-13 

during engine warmup in an automotive diesel engine 

3.4 Effects of fuel aromatic content on particulate emissions: 3-19 

steady state vs. transient tests on a heavy-duty engine 

3.5 Regressions of particulate emissions vs. fuel aromatic content 3-24 

from a nunber of studies using different light-duty engines 

3.6 Regression of particulate emissions vs. fuel aromatic content 3-26 

canbined data from a nwfcer of light-duty engine studies 

3.7 Effect of changes in ccopression ratio on fuel consumption and 3-28 

smoke 

3.8 Regression of particulate emissions vs. fuel 90 percent point: 3-31 

cent ined data from a mutoer of light-duty engine studies 

3.9 Effects of 90 percent point on particulate emissions: transient 3-33 

vs. 13-mode steady-state cycle 

vii 
P.9 

5.1 Refining cost vs. aromatic content of diesel fuel from the 5-11 

Bonner and Moore study 

viii 
P.10 

LIST OF TABLES 

2.1 ASTM criteria for grading of distillate diesel fuel 2-12 

2.2 Ccnparision of ASTM and other specifications for diesel fuel #2 2-14 

2.3 Statistics on selected diesel fuel properties by region 2-23 

4.1 U.S. Refinery product demand: 1987 4-7 

4.2 Refinery product demand by regions ,.. 4-8 

4.3 Refinery inputs: 1987 4-9 

4.4 Prices of raw materials and refined products: 1987 4-11 

4.5 Refined product specifications 4-12 

4.6 U.S. Refinery processing capacities: 1987 4-14 

5.1 Refining cost model results for PAEDs I through IV 5-5 

5.2 Refining cost model results for PAID V 5-6 

5.3 Refining cost model results for the entire U.S 5-7 

5.4 Fuel costs, maintenance benefit, and cost-effect!veness of 5-19 

regulations for a typical light-duty car or truck --.--. 

5.5 Fuel costs, maintenance benefit, and cost-effectiveness of 5-20 

regulations for a typical light-heavy duty truck 

5.6 Fuel costs, maintenance benefit, and cost-effectiveness of 5-21 

regulations for a typical medium-heavy truck 

5.7 Fuel costs, maintenance benefit, and cost-effectiveness of 5-22 

regulations for a typical line-haul truck 

5.8 Fuel costst maintenance benefit, and cost-effectiveness of 5-23 

regulations for a typical transit bus 

ix 
P.11 

PREFACE 

This document is the final report of an investigation of diesel 

fuel quality effects on emissions and of the feasibility, costs, 

and benefits of a nationwide diesel fuel standard for emissions 

control. The desirability of conducting such a study had been 

suggested in previous work by Energy and Resource Consultants 

(Weaver and Miller, 1983; Weaver et al, 1984), in which some 

other aspects of diesel emissions problem were examined. A 

number of engine manufacturers have also expressed concerns over 

deteriorating fuel quality to the EPA. This work was intended as 

a preliminary investigation, in order to identify the issues and 

to determine whether further regulatory attention is warranted. 

The study was conducted as a collaborative effort between Energy 

and Resource Consultants and Sobotka and Conpany, with funding 

provided by the U.S. EPA Office of Policy Analysis. The EPA 

project officer for this effort was Willard Smith. Energy and 

Resource Consultants was responsible for evaluating the effects 

of fuel quality on diesel engines, developing the two regulatory 

scenarios modeled, and carrying out the cost-benefit analysis. 

Sobotka and Company consulted on the development of the two 

scenarios, and carried out the refinery cost modeling. 

The initial project managers for the two firms were Christopher 

Weaver for Energy and Resource Consultants and William Johnson 

for Sobotka and Company. Both project managers left employment 
P.12 

with their respective firms near the end of the project; they 

were replaced as project managers by Craig Miller and Terrence 

Higgins, respectively. Both of the initial project managers 

completed their work on this project as independent consultants 

to their former employers; both participated in the authorship of 

this final report. 

xi 
P.13 

^O-NOWLEDGEMENTS 

The EPA Project Officer for this work was Mr. Will Smith of the 

Office of Policy Analysis. The authors wish to express their 

thanks to him both for arranging the funding for the work and for 

his continuing interest and support during the project. 

In conpiling this report, we have drawn on many discussions, both 

formal and informal, with numerous interested parties. These 

have included refiners, automotive manufacturers, additive 

suppliers, independent consultants, and State and Federal 

regulatory agencies. In addition to providing data, these 

discussions have provided a valuable chance to air preliminary 

conclusions, bring out hidden issues and concerns, and otherwise 

refine the analysis. We gratefully thank all of the parties 

involved, but especially John Wall of Chevron Research, Don 

Dowdall of Caterpillar, Lou Broering of Cuomins Engine, Charles 

Hudson of International Harvester, Richard Lucki and Barry Cahill 

of Peugeot, and Doug Decker and Macie LaMotte of the Colorado 

Health Dept. Their information and assistance have been 

invaluable. However, none of these persons is responsible for, 

nor do they necessarily agree with, the conclusions expressed. 

xii 
P.M 

1.0: iNnracncM 

Diesel engines in light and heavy-duty vehicles emit significant 

amounts of oxides of nitrogen (NOK) , particulate matter, sulfur 

oxides, and unburned hydrocarbons. Emissions levels for these 

pollutants are strongly affected by the quality and composition 

of the diesel fuel used. This study briefly reviews the 

available data and examines the feasibility, costs, and 

cost-effectiveness of reducing diesel emissions by mandatory 

changes in diesel fuel composition. Two types of changes are 

considered: a drastic reduction in diesel fuel sulfur content, 

alone or in combination with a moderate reduction in the fraction 

of aromatic hydrocarbons in the fuel. Effects on engine 

durability, fuel economy, and refining costs are considered along 

with emissions effects. 

1.1 fyqainun iwimuTifM 

The nature and quality of the fuel being burned affects the 

emissions frcm virtually every class of engine. In diesel 

engines, these effects can be either positive (resulting in 

reduced emissions) or negative, depending on the fuel and the 

1-1 
P.15 

engine. In the last decade, disruptions in the supply of oil and 

rapid increases in its cost have led to the widespread use of 

heavier and higher-sulfur crude oils, with a consequent 

deterioration in ignition quality, sulfur content, and other 

indices of diesel fuel quality. Increases in diesel fuel 

consumption relative to gasoline, and phase-out of lead 

antiknocks in gasoline have also contributed to this trend. Most 

knowledgeable observers anticipate that fuel quality will 

continue to deteriorate in the future if market forces are 

permitted to operate freely (McMillan (ed.), 1983). 

The prospect of further degradation in fuel quality has generated 

concern for the possible effects of these changes on emission 

levels. At the same time, concern over diesel emissions in 

general has led to the establishment of stringent new emissions 

standards for oxides of nitrogen (NOx) and particulate material 

from new light-duty diesel vehicles and heavy-duty diesel 

engines. The steps taken to meet these requirements will place 

new demands on fuel quality. For example, the changes in fuel 

injection timing in heavy-duty engines required to conply with 

the NOx standard will make them more sensitive to ignition 

quality than heretofore, and contaminants such as sulfur and ash 

have complicated the development of trap-oxidizers for 

particulate control. 

The establishment of emissions standards for new vehicles has 

1-2 
P.16 

also focussed attention on emissions from the significant number 

of existing diesel vehicles that will not be affected by the 

standards. Improving diesel fuel quality is one apparently 

reasonable approach to reducing these emissions, and has 

attracted considerable attention for this reason. For instance, 

the California Air Resources Board (CARB) has recently 

established a limit on sulfur in diesel fuel at 0.05 percent by 

weight in the South Coast Air Quality Managment District, which 

includes Los Angeles. This action was taken to reduce SO 

2 

emissions and ambient particulate levels. 

The CARB standard of 0.05 weight percent sulfur is one-tenth of 

the present (non-binding) standard for #2 diesel fuel established 

by the Ane ri can Society for Testing and Materials (ASTM). The 

CARB is presently considering extending this standard to cover 

the rest of California. Further limitations on aromatic content 

and/or volatility characteristics are also being considered to 

provide additional particulate control. 

i.2 anmgjQf THE APPBOKH 

The work reported here was intended as a preliminary evaluation 

of the feasibility and cost-effectiveness of diesel emissions 

control through fuel modifications. The purpose of this 

preliminary study was to identify the major issues and to roughly 

1-3 
P.17 

quantify the costs and benefits of some potential fuel 

modifications in order to determine whether this approach shows 

sufficient premise to warrant further regulatory attention by 

EPA. 

The work of the project was divided into four tasks. The first 

and most time-consuming task was a thorough review of the recent 

technical literature dealing with diesel fuel properties; fuel 

effects on emissions, durability, and performance; and related 

topics. This was supplemented by numerous telephone and 

in-person discussions with refiners, engine manufacturers, and 

other knowledgeable parties. The results of this review are 

reported in Chapters Two and Three. Chapter Two presents an 

overview of diesel fuel conposition and quality issues, ami sets 

the stage for the more detailed discussions to follow. Chapter 

Three contains a detailed discussion and synthesis of the 

available data concerning fuel effects on emissions. 

The information developed in Task One was used in Task Two to 

develop two scenarios for improvements in diesel fuel quality. 

The first scenario consisted of a reduction in the sulfur content 

of diesel fuel to 0.05 percent by weight — the same level 

mandated by the CARB. A linear-program refining cost model was 

used to estimate the cost to the refining industry of achieving 

this reduction. Somewhat surprisingly, the model results showed 

a substantial decrease in aromatic content (from 28-30 percent to 

1-4 
P.18 

20 percent by volume) due to re-optimizing for low-sulfur fuel. 

A second scenario, including low sulfur plus a further reduction 

in aromatic hydrocarbons to 17 percent, was also modeled. 

Chapter Four contains a description of the model used and the 

assumptions which went into it. 

In Task Three, the model results from Task Two were cent ined with 

the information gathered in Task One in order to assess the 

effects of each fuel-quality change on emissions, durability, 

fuel economy, and costs. The results of this assessment are 

contained in Chapter Five. Chapter Six, the final chapter, 

presents the conclusions of this analysis and reconmendations for 

further action by EPA. These conclusions are briefly sunmarized 

in Section 1.3 below. 

1-5 
P.19 

1 a >ujrR nrMrri^fi^ m? TOR gnny 

The major conclusions of the study were the following. 

(1) The most important emissions-related properties 

of diesel fuel are the sulfur content and the 

fraction of aromatic hydrocarbons. Reducing fuel 

sulfur would reduce SO emissions and the sulfate 

fraction of diesel particulates, and would 

indirectly reduce ambient levels of sulfate 

particles. Reducing fuel aromatic content would 

reduce the carbonaceous fraction of diesel 

particulate emissions. Contrary to ccomon 

belief, changes in the distillation temperatures 

(such as the 90 percent point and end point) have 

little potential for emissions control. 

(2) The sulfur content of automotive diesel fuel 

could be reduced from the present average of 

about 0.274 percent to 0.048 percent, without 

reducing the availability of diesel fuel, and 

using only the present capital stock. This would 

require segregating production of diesel fuel 

from that of distillate burner fuels, as well as 

high rates of utilization of existing 

desulfurization capacity. The increase in 

average refining cost due to desulfurization 

would be about 1.2 cents per gallon. The average 

aromatic content of the fuel would also be 

reduced by desulfurization from the present 28.7 

percent to about 20.3 percent by volume. 

(3) Reducing the sulfur content of diesel fuel would 

significantly reduce corrosive wear and deposit 

formation, extending engine life and reducing 

maintenance costs. A conservative estimate based 

on the limited data available indicates that 

these savings would be about four times the 

increase in refining costs. Lowering the sulfur 

content would thus result in significant net 

Savings tO society «w«n iynnriny tho 

<>nvirmmpnt«i tvmafiti. The lower aromatic 

content due to desulfurization would also inprove 

cetane nunbers and ignition quality, reducing 

cold starting problems and noise. 

1-6 
P.20 

(4) It would be feasible to reduce aromatic content 

to 17 percent by volume using the present capital 

stock. This would increase refining costs by 

about 0.4 cents per gallon beyond the cost of 

desulfurization. The incremental cost of 

particulate control by this means would be about 

$5.50 to $10.00 per pound of particulate matter 

eliminated. 

1.4 UMITATICre AM) CAVEATS 

The conclusions of this report rely heavily on estimates of the 

reduction in wear rates due to use of low-sulfur fuel and of the 

reduction in particulate emissions due to lower aromatic 

content. Neither estimate is wholly satisfactory, due to the 

limited data available. These data are sufficient to establish 

the direction and approximate magnitude of the effects, but the 

estimates could be inproved by better data. Further research on 

the effects of low vs. moderate sulfur fuels on engine life 

would be highly desirable, as would additional carefully-designed 

studies of the relationships between aromatic content and 

particulate emissions in a variety of heavy-duty engines. 

The conclusions also rely heavily on the results of a 

linear-programning model of the U.S. refining industry. This 

model has been used extensively before, and is considered to be 

reasonably reliable. The aggregated nature of the model results 

in some over-optimization, however, so that the actual refining 

1-7 
P.21 

costs experienced would probably be somewhat higher than the 

model predicts. The effects of this problem have been minimized 

by taking the results only as the difference between two model 

runs — thus, only differences in the degree of overoptimi zation 

between the two runs would affect the results. One area where 

this may have occured is in the usage of distillate 

desulfurization capacity. The model indicates that demand for 

low-sulfur diesel fuel could be met using only the existing 

capacity, but a very high rate of utilization was required. In 

reality, some refineries might have to invest in a small amount 

of new capacity, which would increase the costs of 

desulfurization somewhat. 

The model is also limited to accounting for changes in refinery 

operating costs. Changes in distribution and marketing costs due 

to the segregation of diesel fuel from burner fuel oil were not 

accounted for, and we were unable to quantify these costs. They 

are believed to be small, however, when compared to the increase 

in refining costs. 

1-8 
P.22 

2.0 : niESET. BTTRT. CUALITY AM) COffOSITICN 

Diesel fuel is a cooplex substance, surrounded by an equally 

complex set of definitions, quality indices, test methods, and 

standards. This chapter reviews the composition and properties 

of automotive diesel fuels, discusses the indices of fuel quality 

now in use, reviews the currently applicable fuel-quality 

standards, and discusses current and projected quality trends. 

This review is intended primarily to establish the necessary 

background for the sections which follow; it is by no means 

complete. More complete discussions are available in Dorn and 

Mourao (1984) and Lilly (1984), among others. 

2 . 1 fTwPnRTTTfW UsW) PHnPERTTES CV ACTiTMnrnVE nfESET. FTTET. 

All petroleun-derived liquid fuels are cooplex blends of 

different hydrocarbon species. Automotive diesel fuels are 

composed of hydrocarbons which boil at teaperatures between about 

300 and 700 F. This range falls between that of gasoline (which 

is a mix of light hydrocarbons) and heavy gas oils. Diesel fuel 

is separated frcm the lighter and heavier hydrocarbons in crude 

oil by distillation, and is thus a "middle distillate" fuel. 

2-1 
Other middle distillate fuels include jet fuel, kerosene, and 

several grades of distillate fuel oils for boilers and other 

stationary combustors. 

The diesel fuel sold in the United States is of three types, only 

two of which are used for highway vehicles. Diesel #1 contains 

hydrocarbons boiling between about 180 and 250 C, while diesel 

#2, a heavier fuel, contains hydrocarbons boiling between 200 and 

350 C. Diesel #1 is most coomonly used as city-bus (C-B) fuel, 

since bus fleets — which pay a premium for it because it 

produces lower smoke emissions — are its primary users. Due to 

its lower viscosity, diesel #1 is also used in very cold weather, 

or for blending with diesel #2 for cold weather operation. 

Diesel #2 is used by highway, farm, and construction vehicles for 

almost all other purposes, and accounts for the great 

preponderance of fuel sold for automotive use. Diesel #4 is a 

still heavier fuel which is used in railroad, large stationary, 

and some marine engines, but not in highway vehicles. 

This report deals only with diesel fuels used for highway 

vehicles, and concentrates on diesel #2 as the most important of 

these. In addition to the far greater usage of the #2 grade, 

diesel #1 is already perceived as (and priced as) a premium fuel, 

and has thus been less subject to deterioration in quality. 

Diesel fuel is made up of three primary types of hydrocarbons: 

2-2 
paraffins (straight-chain hydrocarbons), napthenes (also known as 

cycloparaffins), and aromatics. The three groups are 

distinguished by their differing molecular structures, which in 

turn lead to different physical and chemical properties. These 

property differences affect the combustion process, and thus 

affect engine performance and emissions. 

Figure 2.1 shows some typical molecules of each of the three 

hydrocarbon groups. The aromatic hydrocarbons are distinguished 

from the other two classes by the presence of one or more 

"benzene-ring" structures, composed of six carbon atoms strongly 

bonded into a hexagon. They can be distinguished from the 

napthenes, which also have a ring structure, by the fact that the 

carbon atoms in the napthene ring are each bonded to four other 

atoms (two carbon atoms in the ring and two hydrogen or 

"side-chain" atoms). The carbons in the aromatic ring are bonded 

to only one hydrogen or side-chain atom, rather than two. This 

strengthens the carbon-carbon bonds in the ring structure itself, 

so that aromatics do not burn as readily as napthenes or 

paraffins. 

The hydrocarbons in diesel fuel differ in volatility as well as 

chemical in structure. Volatility is closely related to the 

molecular weights of the hydrocarbon species involved. Lighter 

hydrocarbons boil and can be distilled off at a lower 

temperature. The boiling point of a fuel sample increases with 

2-3 
P.25 

(.ont-r.il 

<r"un Tvne l-urmulu i" Lxamplc Structur e 

In 

iMrafftnas

 r

N

M

:sf^

 C16H

1« oi J -(ni J ) 1 4 -on J 

CH—-ai . 

Monocvclop.traff Ins "^' N ''ld^l' 1 \ / 

CH 

3 

a"i7 

' u 

Cll. 

IllcyrJoparur.l.m C^. , «:, A " 3 0 0~y c „ 

rrlccvclop.r.ffln.s l^ll,. ^ C^H,,, Q-Oai , 

III, \- ^ 

Bonzeuo. C^H ^ C,,^ , CHj 

T«"alln» C„H,N_8 rlfc ll, 4 «:H,]Q U 

N.prh,l„ii„ SM2N-12

 CI6M

20 "'©Ov, 

Figure 2.1: ClassaM of hydrocarbon Molecules found in diesel fual 

(Hilden et alia, 1962). 

2-4 
P.26 

prolonged distillation, as the lighter of its constituent 

hydrocarbons-boil off first. This is used to provide a 

convenient way of characterizing the mix of molecular weights in 

a fuel, by means of the "distillation curve". The distillation 

curve is given by specifying the initial boiling point, the "10 

percent point" (the teaperature at which 10 percent of the mass 

has boiled away, (at atmospheric pressure) the 20 percent point, 

and so forth up to the 90 percent point and the end-point, which 

is the temperature at which all of the fuel has evaporated. The 

10 percent, 50 percent, and 90 percent points (reflecting 

"front-end", average and "back-end" volatility) generally receive 

the most attention. 

In addition to the hydrocarbons which are its primary 

constituents, diesel fuel also contains a small amount of 

organically-bound sulfur. The amount of sulfur is dependent on 

the sulfur in the crude oil and on refining procedures. In 

diesel #2, sulfur generally constitutes about 0.1 to 0.5 percent 

of the fuel by weight. Organic coapounds of other elements such 

as nitrogent vanadium, aluminum, cobalt, lead, and barium are 

also present in trace amounts. 

The conposition of any particular batch of fuel is determined by 

the properties of the crude oil it was refined from, the 

capabilities of the refinery, and the competing demands of the 

other fuels that are being refined simultaneously from the same 

2-5 
P.27 

crude. In addition to diesel fuel, other fuel types compete for 

the "pool" of-hydrocarbons available in the middle distillate 

range. These include #2 burner fuel oil (which is physically 

very similar to diesel #2) and jet fuel. To save on tanking and 

other costs, many refiners and distibutors have combined diesel 

#2 and #2 burner fuel as the same product, although the quality 

requirements for burner fuel are less stringent than those for 

diesel. This results in some "give-away" of fuel quality 

("give-away" is defined as producing a fuel of higher quality 

than needed to meet specifications). 

2.2 PTFfiFJ, FQEL CPALITY INDICES 

The quality of diesel fuel is most often measured in terms of its 

cetane nuaber. The cetane nunber is a measure of the ease or 

difficulty of igniting the fuel when it is injected into the 

combustion chamber. High-cetane nunber fuels ignite readily; 

low-cetane fuels take longer to ignite. Cetane is most important 

for engine starting at low temperatures, when a fuel with too low 

a cetane rating may not Ignite at all. A warmed-up engine will 

run on fuels with much lower cetane ratings than it will start 

on, but too low a cetane still affects engine noise and fuel 

economy. 

Cetane nunber is measured by comparing the ignition qualities of 

2-6 
a fuel against those of standard mixtures of cetane (which has 

very high ignition quality) and heptainethylnonane (which has poor 

ignition qualities). Since this test is expensive, the "cetane 

index", which can be calculated from the physical properties of 

the fuel, is often used as an approximation of the cetane 

number. This index contains considerable error, however, and it 

is not applicable to fuels containing cetane improving additives 

or to non- petroleum-derived fuels. A cetane number (or cetane 

index) of 50 to 55 indicates a premium quality fuel, while one 

from about 45 to 50 is good quality. The Ane ri can Society for 

Testing and Materials (ASTM) standard for diesel fuels #1 and #2 

specifies a minimum cetane number of 40. 

Cetane nunber and ignition quality are closely related to the 

hydrocarbon conposition of the fuel. Generally, paraffins ignite 

more readily than napthenes, which ignite more readily than 

aromatics. The effect of aromatics on cetane is especially 

strong. Figure 2.2 shows the relationship between cetane number 

and aromatic content for a large saaple of diesel fuels. 

Within each class of hydrocarbons, heavier (higher molecular 

weight) hydrocarbons ignite more readily than lighter ones. This 

probably accounts for the outlying points in Figure 2.2. The 

relationship between aromatics content, molecular weight, and 

cetane is also the basis for the cetane index calculation. This 

calculation uses the density and 50 percent point of the fuel. 

2-7 
P.29 

TOTAL PARAFFINS. vol% 

100 90 80 70 60 50 40 30 

cc 

UJ 

m z 

z 

UJ 

UJ 

o 

o 

UJ 

> 

tc 

LM 

tA 

a. 

o 

70 

60 

50 

40 

30 

20 

o 

o 

-

T r-- t i 

o 

0 

o 

o 

o o o oW ,£ 

0

 °°0a «** o « o _ 

o o 

o 0 o 

o o 

J 1 fi 1 1 

-T r 

0° 

1 ° 1 

-

-

• 

0 

0 

10 20 30 40 50 60 70 

TOTAL AROMATICS. vol% 

Figure 2.2: Relationship between aroaatic content and cetane nuaber 

(Glavincefski et alia, 1984). 

2-8 
P.30 

Conditions during the cetane rating test resemble those in an 

engine during cold starting, and the present test does appear to 

give a reasonable measure of cold-start properties of fuels. 

However, there is a growing consensus (McMillan (ed.) 1983) that 

the present cetane measurement does not adequately measure the 

ignition properties relevant to today's engines in normal 

operation. A recent study by Barry and co-workers (1985) showed 

almost no effect of cetane number on ignition delay. In 

addition, numerous studies have shown that diesel engine 

emissions are more closely correlated with the aromatic content 

of the fuel than with its cetane nunber (although the cetane and 

aromatics content are themselves closely correlated). Although 

alternative measures have been suggested (Plee and Ahmad, 1983; 

Wade et alia, 1984) there is as yet no widely accepted substitute 

measure for overall ignition quality in modern diesels. 

Two measures which are related to the cetane nunber are the 

volune fraction of aromatic hydrocarbons in the fuel and the 

aniline point* The measurement technique for aromatic content is 

defined by ASTM procedure D-1319, which uses fluorescent 

indicator absorbtion, abbreviated FIA. Most studies of fuel 

effects on emissions have found a better correlation with FIA 

aromatic fraction than with cetane number. The aniline point is 

the teaperature at which pure aniline becomes miscible with the 

fuel, measured in accordance with ASTM procedure D-911. This is a 

2-9 
P.31 

fast and simple measure of the aromatic and napthenic character 

of the fuel, and has been found to correlate well with cetane 

nunber (Collins and Unzelman, 1982; Steere, 1984). 

Cetane nunber (like octane nunber for gasoline) is the most 

coomon and visible quality indicator for diesel fuel. Other fuel 

properties which are often specified include the back-end 

volatility (90 percent point or end point), sulfur content, 

viscosity, density, cold-flow properties, copper-strip 

corrosivity, and Conradson carbon content (a measure of 

coke-forming tendencies). Density, viscosity, and back-end 

volatility are all determined by the hydrocarbon makeup of the 

fuel, but sulfur and (to an extent) cold flow properties can be 

independently varied. Sulfur content can be reduced by 

hydrotreating, while cold flow properties can be improved by cold 

flow improving additives. 

At low teaperatures, the long-chain paraffins in diesel fuel 

condense to form wax crystals, which can block the fuel filter. 

At still lower temperatures, diesel fuel gels conpletely. Cold 

flow properties such as the cloud point (the teaperature at which 

wax crystals first appear in the fuel), the pour point (the 

teaperature below which the fuel will not flow), and the cold 

filter plugging point (referring to a specific test of flow 

through a fuel filter) affect the ability to start and run at low 

teaperatures, and are very important for operation in cold 

2-10 
P.32 

climates, but have little significance for engine operation 

otherwise. They are determined by the content of long-chain 

paraffins in the fuel (which is related to the back-end 

volatility and the overall paraffin content). 

There is a trade-off between cetane and cold-flow properties: 

highly paraffinic fuels, which have high cetane numbers, also 

tend to form wax crystals more easily. This problem can be 

alleviated by dewaxing (an expensive process) or by the use of 

cold-flow improving additives, which hamper the formation of wax 

crystals. Refiners also typically increase the amount of light 

hydrocarbons and reduce the back-end boiling point in winter to 

provide better cold-weather performance. 

2.3 CURRENT FUEL QUALITY STANDARDS AND REGDLATIONS 

The criteria which define the different grades of diesel fuel are 

set by ASTM Standard D-975. These criteria are reproduced in 

Table 2.1. The ASTM is not a government agency, and its standards 

have no legal force, but they are widely adhered to. A few 

states have established legal requirements for diesel fuel; 

except for California, these generally follow the ASTM 

guidelines. California has established a limit of 0.05 weight 

percent sulfur in diesel fuel sold in the South Coast Air Basin, 

and is considering extending this requirement to the remainder of 

2-11 
I\> 

I 

Otode e< MOM I Pttal ON 

No. ID A voiotfe ditlilol. luel oil lor 

«agin.t in Mrvic. (.quiring lr.qu.nl 

ipaad oad load chaogn. 

No. JO A diililut. tool od al loww 

valolility lor taginat la industrial aod 

boavy n^ile service. 

No. 4 0 A IIMI oil lot low and loadime 

•pud lagi.st. 

Math 

Point. 

•c 

Mia 

. 38 

(IM I 

S3 

11231 

JS 

0301 

Cloud 

Point. 

•c 

Iti 

M o i 

m 

m 

Wolor 

aod 

Sodt-

% 

Man 

0.05 

0 05 

O.SO 

Carbon 

Residue 

aa, 10 

porous 

R.aldtnan. 

% 

M O M 

O IS 

0.35 

Aab. 

weight 

% 

Man 

0.01 

0.01 

0.10 

Tsmpaiebnet, 

•wn 

• 0 % Petal 

Mia 

7tr 

|S40| 

M O M 

5 8 B 

IS30I 

338 

16401 

Viscosity 

Waaaiatk tt l 

«MVI > 

et40° C 

Mia 

1.3 

1.9 

S.S 

Maa 

3.4 

4.1 

34.0 

tayboH. SUS 

al IM°P 

Mia 

33.6 

45.0 

Ma« 

3 4 4 

40.1 

135.0 

Mw, ' 

walgbt 

% 

Maa 

0.50 

0.50 

2.0 

Cappot 

Strip 

ConoMaa 

Na. 3 

No. 3 

1 

Ctlaa t 

bar 

Mia 

40> 

40> 

30< 

* To mo.1 ip.cial oporoliag cenditieat, aioditicatiaat ol indivi 

may be ograad upon between pwchoMt, itltr, ond manulaclMt«f. 

k

 It h unteofttlic to tpecity low-ltwipetoluto prop*ti«t dial wil 

aa a brood botit. SaMtloctory epewiben thoUd be achieved ia moil 

lot waa gppontoaco point) It tpodlwd at A*C IIO'FI abov. lh. tt 

oatbiMl Itwpsiuluiot lot aW anadrt ol October. Novmbtt. 

and March at. givn in ASTM 0 975 in maps lor lb. 41 conliguout 

guidance it el a gtnsinl notor.) taaw nuipintnl datignt. M M ol I 

ridual limiting r«quit«eienlt 

< WbM dood point Utt tl 

1.7 cSl and * • 90% point i 

pioptitill thould be agreed < 

uso and eapocled ombienl tetnpatolwfei 

i -I2* C |I0"F| it tpecilied. dt. M M 

• bo waived. 

tatitlocloty operation 

cotot il lh . cloud point 

iMtlb percentile miniamei 

leant percentile minimMn 

January, February, 

tlaiet and Alatio thii 

tow Iwptonei additiv.t, 

point luelt. Appropridi . IIM I tupplier 

vitcotity 

' In couatriet ouitide lb. U.S.A., olhm MiHur hnilt mas/ apply. 

• What. clan . numlm by Malbod 0 dl 3. it not o.oiiobU. ASTM M.lhod 0 976. Cakulolad 

C.Ian. Indaa ol Dittilol. f uoh any bo utad at an opptoaininlio.. What. <Mrt it ditograomonl, 

Mediod 0 613 thai b* d » nloro. mediod. 

1

 low onooiphtrie Iteipsrolurss at wt at tngint operation at high alliludei may raquire 

uto ol loab) widi highat ctono rotingt. 

• MilwMtw tquarad p « tocond loiKciol SI unil) (Not*. 1 cSl ~ I am'/i). 

k

 Th. vobnt in SI wdtt at. to b . ngardVd at di . ttondord. Th. vahMS in U. S. cuilnwnry 

imitt at. lor information only. 

• Nadiing ia dat tpacrlicaaoa dial ptadud. abtwvaac. ol lodoral. Hole, ot local ragulaliaai 

•y b. an t totitictiv. 

Table 2.1 : ASTM criteri a for grading of distillat e aiese l fuel (SAE, 1984). 

I 
the State (GARB, 1985). There is presently no Federal-level 

regulation of diesel fuel quality. 

The criteria set by ASTM D-975 allow for a great deal of 

variation in quality. Both a very good fuel and a very poor one 

may conply perfectly with the ASTM specifications, but produce 

radically different performance in use. Table 2.2, reproduced 

from the current SAE Handbook, compares the ASTM specifications 

for diesel #2 with those established by the U.S. military, by a 

nunber of foreign governments or standard-setting organizations, 

and by EFA for fuel to be used in emissions certification 

testing. 

This latter specification is of especial interest, since diesel 

engines are required to meet emissions limits only when running 

on certification fuel. As these.limits (especially the NO K 

limit) are tightened, engines will become more sensitive to fuel 

quality (Weaver et al, 1984), and the use of fuels outside the 

EPA specs but within those of the ASTM could result in 

significantly greater emissions than would be predicted by the 

certification test. 

2.4 TTOfB TN PIEfiFJ, i m ffltVLUX 

Figure 2.3 shows the trends in the nationwide averages of a 

2-13 
rs) 

I 

C.ton. Numb.i 

Sullur, matt % 

DiililatKxi 

T«apwatufe, °C 

50% Poml 

65% Point 

85% Poinl 

90% Poinl 

End Poinl 

Kmoaaotic 

Vitcotily. cSl 

ol20"C 

0130-C 

ol40*C 

Owitily. g/ml 

at IS'C 

ASTM 

097S 

OtMate 

NI.1- D 

40 mix 

O.S M I 

382-338 

1.9-4.1 

— 

U.S. 

Padoral 

VV-P-8Q0C 

•radeOP- 1 

C*>CMM 

(U.S., 

45 mia 

0.5 mas 

teport 

338 moa 

370 maa 

1.9-4.1 

report 

Ocanut 

(Ovaeeaas) 

45 min 

0.7 maa 

report 

357 moa 

370 ana 

18-9.5 

l.V-5.5* 

0.815-

0.860 

Caesataeclal Pools 

Canada 

cost 

Staadard 

CAM3-3.6-M83 

Typos •.C O 

40 min 

0.7 moa 

360 maa 

1.4-4.1 

— 

U.K. 

•tttith 

Slaadeid 

last. 

MM6 9 

Oaa . A 1 

SO tnin 

0.3 m i 

350 moa 

157- moa 

1.5-50 

-

Oetm aay 

.taaoatas 

CaeamlHaa 

lot 

Tetting 

U N SIM I 

45 min 

0.3 mai 

250 min 

350 maa 

357amoa 

3.0-8.0 

I.S*-4.S« 

0.815-

0.855 

Australia 

Ak* 

PPTC 

Au*oataolva 

IHaeal 

tv-i 

45 min 

OS moa 

357 moa 

365* maa 

1.5-5.S 

-

iapo. 

MS 

Ktt M 

OradoM O 

45 mm 

0.5 moa 

350 moa 

2.5 min 

2.1'min 

— 

IPA 

tehaast 

Tetliag 

Typ.2- 0 

42-50 

0.2-0.5 

243-283 

388-321 

304-349 

1.9-3.1 

0.S4O0.860 

Tast Paa!* 

U.S. 

1 

Military 

Beleroa 

Otade 

Meta l Pu.1 

MM.-P-46I628 

40-43 

0 95-10 5 

245-285 

330-357 

383 maa 

1.9-4.1 

report 

h~p . 

KM 

lalottd 

Transport 

CoaMttlttaa 

•elorattca 

Pwoi 

•F-83-A-80 

3I-S7 

0.2-O.S 

245 min 

330-340 

370 M I 

2 5-3.5 

0835-0.845 

• tttimeltd tryivelteri nal port el tpecilitelien. 

r

"'e *•*'• cTs^'^;i.flSTK •* °< - «if.=-.«m ro,...„.,.',.., ,2 

J 
P.36 

•am'i 

LSI 

].<• 

).M 

w Ji l 

|}.t l 

I I.M 

£2.9* 

8 2.11 

|i.7 I 

8 2.68 

It* 

2.«* 

2.3* 

2.2* 

2.tt 

iMTitmilC ulStOsirr 

ri 

L_l _ 

, 4 

' 

s-4— 

T 

i 

i = f-t -^-

.. i 

~> 

• < 

1 

! 

• 

i

! 

i 

1 •i^-tt J -i TH ilsi'-L 

r

*t' -

IL IP i 

; 

t 1 

1 

! i ! 

•Jl 

e.s* 

S 

3 

<g 4.2* 

4.11 

o.a* 

3U.FU* fWTOir 

t 

— 1 -

l l 

! ! 1 

1 ! 1 1—r 

i 

1 

! 

1 — 

1 

1 

1 

1 

1 

1 

I 

l i u ftfp 

1

 1 .1-.'*- '• 

1 

1 1 

1 

1 

1 

Ll 1 1 P

f 

s 

i fM 

S m 

= S7» 

° wa 

«* 

sg« ma t 

i~* •i-"-

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rf-l r M — l

-i 

• • •• 

.11 -

^ 

f

-fl • r-r 

r 

L_ 

Sa 

IT* * mm 

V 

Sl | _ _ . . 

U .1. ",'T,M,-

I

L., .,, 

It

 1l

-

, r " 

L L 

4tl 1 1 1 1 1 1 1 1 1 1 1 

! 

— — _ —_li_^ ' 

:_: _ cz32_ ^r-

^ 

_ 

1 1 

«3f 

4 M 

3H 

tai HURT 

M tn L 

»~ q 

11 

-P-s 

r r 

Figure 2.3i Trends in soae properties of type T-T and grade 2-D 

diesel fuel oils (Shelton and Dickson. 1984). 

2-15 
number of properties of diesel #2 (or truck-tractor fuel — the 

classification was changed in 1979) since 1960. As this figure 

indicates, the last two decades have seen a steady decline in the 

average cetane nunber of the fuel sold, and this decline has 

become especially marked since 1976. This decline has been due to 

a marked increase in the average fraction of aromatics in the 

fuel. Endpoints and 90 percent points have increased markedly as 

well, and sulfur content has increased somewhat as well. These 

graphs are based on the annual surveys conducted by the National 

Institute for Petroleum and Energy Research (Shelton and Dickson, 

1984). 

Other surveys, such as those of the Motor Vehicle Manufacturers 

Association (Pless, 1984) have shown an even greater increase in 

sulfur content and in aromatics in recent years. Figures 2.4 

through 2.8 show the trends and distribution of aromatic content, 

cetane index, 90 percent point, API gravity (which is inversely 

related to density), and sulfur from the MVMA surveys. These 

data show a substantial increase in both aromatic content and 

sulfur content since 1980. Data for aromatics were not available 

in 1983, but the continuing increase in density and decrease in 

cetane index during 1983 indicates that the aromatic content 

continued to increase. 

This general decline in diesel fuel quality is due to the need to 

process heavier and lower-quality crude oils as more desirable 

o_i a 
AO 

38 

Z 36| 

UJ 

<J 

or 

UI 34.1 

F 

UJ 

321 

> 30j 

(J. t 

F 28; 

< 

< I 

24E 

22: 

P.38 

MVMA. SUMMER SURVEYS 

P£RC£iVT <7r* r"</tUS * T <7rt ABOVE 

M M MMMM M M 

Mt 

m 

m OA ! • ffi IB 

3: 

p 

3 : 

£ 

Eft 

Si 

m 

m 

m 

m SH 

a=F=< 

-*+ • e £ 

^ ^ = 

mm 

o «v 01: 

i i y 4/; 1 1 

1 2 T **wr M JO 

ta ta to JO to 

p£RC£NT OP FVtLS Ar CR Q&LOW 

-T=TK t> ' tt t* 

Figure 2.4» Distribution of diesel fuel aroeatic content frota tht 

MVMA sueeer surveys (Pless, 1984). 

2-17 
P.39 

MVMA SUMMER SURVEYS 

p£ftc«rv-r OF FU&LS Ar OR ABova 

ra «s M <d M n A-ofa j ! 

i •! 

pe.RCc.Nr OF F<J£LS Ar OR. B^LCW 

Figure 2.5» Distribution of API gravity of diesel fuels froe the MVWA 

suaaer surveys (Pless, 1964). 

2^18 
P.40 

MVMA SUMMER SURVEYS 

p£RC6fi/r OF FUELS AT OR ABO\/a 

n m M ta » 

H M tt 

pe.Rce.nr OF FU&LS Ar OR BSLOW 

Figure 2.6: Distribution of calculated cetane index of diesel fuels 

froa the MVMA suaaer surveys (Pless, 1964). 

2-19 
P.41 

MVMA SUMMER SURVEYS 

p€RC£Hr OF FU£LS Ar OR ABOV £ 

20 JO « JO M »0 10 

PERCENT Of FU6LS Ar OR BELOW 

Figure 2.7: Distribution of 98 percent point of diesel fuels froa the 

HVMA suaaer surveys (Pless, 1964). 

2-20 
MVMA. SUMMER SURVEYS 

PERCEkr OF FUCLS Ar OR ABOV& 

PIRCEHr OF FU£LS AX OR BELCW 

FigUr V2<a i

 O*«trib«tion of sulfur content of diesel fuel , froa th . at** 

suaaer surveys (Pless. 1964). «*»»•* rueis rroa the MVMA 

2-21 
oil resources are exhausted (Strange, 1982; McMillan (ed.) 1983). 

These lower quality crudes contain more heavy hydrocarbons and 

more aromatics than the higher quality oils. Low-quality crudes 

are usually also richer in sulfur, but the sulfur content of the 

refined fuel has been kept in check by consumer resistance, 

occasioned by the fact that high sulfur fuel has destructive 

effects on engines. The use of low quality crudes has thus 

required an increasing amount of desulfurization treatment for 

diesel fuel and other middle distillates. 

Examination of average numbers does not adequately reflect the 

variation in fuel quality frcm supplier to supplier and from time 

to time. As discussed at greater length in Chapter Three, this 

variation is itself a significant problem for emissions control, 

since engines must be able to cope with an occasional tank of 

very poor fuel without disastrous consequences. Table 2.3 shows 

the minimum, mean, and maximum values in each region for a number 

of diesel fuel properties found by the 1984 NIPER diesel fuel 

survey* Figures 2.3 through 2.8 also show the distribution of 

properties found by the MVMA fuel surveys in recent years. As 

these figures and the table show, a significant fraction of 

diesel fuels now on the market fail to conply with even the lax 

ASTM specifications for one or more properties. 

In the absence of government or other initiatives to the 

contrary, most knowledgeable observers expect that diesel fuel 
TABLE 2. - SUMMARY FOR 2-D FUELS 

Diesel Fuel Survey, 1984 

N> 

I 

M 

m-t 

fafliliwirtqat^ a 

IMMtailHaltiil* 

Maaaharei'teale 

T M 

OeeWtr.'AM 

flaak aalaa.*P 

Catae.A5TM 

W i n III.M.aat.Hc.rfltMlOO-F 

OaaapeM.'r 

fta t Haa . *T 

Mfc><ea«eal,*t«j 

Itta i t. f 

Cll l Ilna a 10*. atm 

Aak.artft 

GaaMaaatker 

Ow.ti e tee 

M a 

Mf. 

H a 

fclpelal 

ASTM 

DMT 

DM 

DlMO 

D446 

DM00 

Df? 

D I M 

M i l 

DM4 

D M t 

D M 

D f » 

DM 

Ml.l-.e t 

M J 

I M 

L U 

I M 

-11 

GO 

0.011 

t i l 

OJM 

OJM 

MO 

MO 

l i t 

» 4 

4M 

4M 

I M 

A3.C 

Dxr.a 

M 

Average 

M.7 

' I M 

I M 

• 

0.2M 

1*11 

0.141 

0001 

441 

M J 

MO 

437 

t i l 

f M 

04* 

Mt.lataa 

43.4 

MO 

U 

4.14 

41 

M 

OUO 

I M A 

OMO 

O.OIO 

t i l 

t i l 

4 M 

U l 

171 

US 

716 

11.0 

140 

U t t 

I I I 

•4 

-If 

oota 

127.0 

0.0M 

oooo 

411 

401 

3 M 

M t 

M7 

M t 

114 

D 

A.B.C.I.K.Q.I 

M 

• Average 

M.4 

'171 

106 

0.236 

I46J 

O I U 

O.MI 

411 

4 U 

M2 

4M 

t i t 

I M 

M l 

Mulan a 

M l 

l i t 

l t 

3.M 

42 

I t 

OMO 

177.0 

OMO 

0.006 

61.1 

MO 

442 

4M 

M2 

M l 

711 

B.P.0 

A.B.C.D.HJJ.K 

Miaiaeai 

M.6 

I M 

L06 

I.M 

J 

60 

0060 

106.0 

0.000 

0.000 

M.O 

112 

l i t 

174 

4M 

4M 

U t 

M 

a Avera#e 

M.» 

' I M 

2.M 

0.266 

1437 

0144 

0001 

41.0 

4*4 

M l 

433 

107 

M t 

M f 

tt-.i — 

41.1 

111 

2.6 

3*0 

42 

16 

0.6M 

177.0 

OMO 

0.010 

t i t 

MO 

442 

4M 

M l 

M l 

711 

H.U.K 

D.K.F.O.UI.N 

Mtaiaaai 

M J 

141 

lil t 

r» 

m 

- It 

out 

I B l 

oooo 

OOM 

41t 

M O 

M l 

406 

4M 

I M 

U f 

M 

Average Huiat a 

M J M J 

' I M I M 

U 

2*1 3 80 

41 

M 

0.370 OMO 

140.1 I& M 

0.OM OMO 

0002 0.010 

461 M l 

4 U 16.3 

MO 4 M 

431 M l 

t i l MO 

• M M7 

M l TM 

UtNAF 

HJ.JX 

M 

Miaaaaa Average Haiiat a 

M l 

140 

U t t 

116 

-40 

46 

0010 

1M.1 

0.040 

OOOO 

M A 

MO 

H I 

4M 

4M 

171 

- fa 

a.i 

•ITI 

123 

0 3 M 

1411 

J I M 

uon 

44J 

46.4 

M7 

461 

u i 

110 

• M 

M J 

M l 

2 6 

430 

41 

41 

OMO 

i t u 

0.140 

0.010 

41.1 

6 71 

M l 

M l 

MO 

M 7 

TM 

Mlataea 

M J 

I M 

L06 

1.M 

-40 

-60 

0.010 

t i l 

OOOO 

0.0M 

MO 

331 

l i t 

374 

4M 

4M 

t M 

Natioaal 

AU 

I M 

Areaj i 

M J 

' I M 

117 

0.267 

143.3 

0134 

0.003 

461 

413 

M4 

431 

613 

102 

•63 

Maaiaaea 

434 

MO 

I t 

474 

a 

46 

0*40 

I M 6 

OMO 

0010 

632 

113 

601 

M l 

MO 

M7 

7M 

Taole 2.3: Distribution'of diesel fuel properties by regions (Shelton 

and Dickspn, 1984). 
P.45 

quality will continue to decline for the remainder of this 

century. Average cetane numbers will decline, and an increasing 

fraction of fuels will fall below the ASTM mininun cetane of 40. 

Similarly, average sulfur content will increase toward the ASTM 

maxinun of O.S percent by weight, and an increasing nunber of 

fuels will exceed that level. Back-end boiling points are 

expected to increase steadily as well, except where they are 

constrained by the needs of cold-weather operability. The 

potential effects of these changes on diesel emission levels are 

discussed in the next chapter. 
P.46 

3.0 : TORT. CTIALITY EFFECTS fM TOPSE.. tTMTvTMBS 

The properties of diesel fuel, the indices by which these 

properties are measured, and the criteria used to define diesel 

fuel quality were discussed in the previous chapter. This 

chapter reviews the effects of changes in the properties and 

composition of diesel fuel on the durability, fuel economy, 

performance, and emissions levels of diesel engines. The purpose 

is to establish an analytical framework against which to evaluate 

the engine and emissions effects of the two fuel-quality 

regulation scenarios discussed in Chapter Five, and to provide a 

starting point for further research in this area. 

Studies of the effects of changes in fuel properties on engine 

performance and emissions are complicated by the fact that few 

changes in fuel properties can be carried out independently — 

there are strong correlations among individual properties, and it 

is seldom clear which is the property of greatest interest. The 

properties singled out for discussion here are those which are 

generally considered (either for theoretical reasons or from 

practical experience) to be the critical ones from an emissions 

and performance standpoint. These are: sulfur content, aromatic 

content and ignition quality, back-end volatility, density, and 

3-1 
P.47 

viscosity. A number of secondary properties can also affect 

emissions, but are generally related to one or more of the 

preceding five. These secondary properties are briefly discussed 

in a final section. 

3.1 ffTEi- CTm*n crwrewr 

Diesel fuel normally contains between 0.1 and 0.5 percent by 

weight sulfur, with the average in 1984 being about 0.27 percent 

according to the NIPER survey (Shelton and Dickson, 1984). As 

discussed in Section 2.4, this average has increased somewhat 

since 1980. The MVMA diesel fuel survey shows an even sharper 

increase in sulfur content, from a median of .19 percent in 1980 

to .31 percent in 1983 (Pless, 1984). 

Fnvlponm»nta1 mttrntitm 

Sulfur in diesel fuel contributes to environmental deterioration 

in both direct and indirect ways. Most of the sulfur in the fuel 

burnt to SO , which is emitted to the atmosphere in the diesel 

2 

exhaust* Because of this, diesels are significant contributors 

to ambient SO levels in some areas, and indirect contributors to 

2 

acid deposition as well. In California's South Coast Air Basin, 

diesels are projected to account for 24 percent of all SO 

2 

emissions, despite a requirement that large refiners market 

3-2 
P.48 

desulfurized fuel (CARB, 1985). Nationwide, diesel fuel accounted 

for about 370 thousand tons of SO in 1985, assuming that 1,245 

2 

thousand barrels per day averaging 0.3 percent sulfur were 

produced. 

Most of the sulfur which is not emitted as SO is converted to 

2 

various metal sulfates and to sulfuric acid during the combustion 

process. Both of these materials are emitted in particulate 

form. The typical rate of conversion in a heavy-duty diesel 

engine is about 2 to 3 percent of the fuel sulfur; and about 3 to 

5 percent in a light-duty engine. Even at this rate, sulfate 

particles typically account for 0.02 to 0.05 g/BHP-hr of 

particulates in heavy-duty engines. The effect of the sulfate 

particles is increased by their hygroscopic nature — they tend 

to absorb significant quantities of water from the air. 

Certain precious-metal catalysts such as those used in the 

Johnson-Matthey wire-mesh trap-oxidizer can oxidize SO to SO , 

2 3 

which combines with water in the exhaust to form sulfuric acid. 

The rate of conversion with the catalyst is dependent on the 

activity of tbe catalyst — catalyst formulations which are most 

effective in oxidizing hydrocarbons and carbon monoxide are also 

most effective at oxidizing SO . The presence of significant 

2 

quantities of sulfur in diesel fuel thus limits the catalytic 

activity possible in the trap, making regeneration more difficult 

(Weaver, 1983; 1984b). Low sulfur fuel would make catalysts and 

3-3 
P.49 

catalytic traps more effective for particulate (as well as 

hydrocarbon and odor) reduction. 

Sulfur dioxide in the atmosphere oxidizes to form sulfate 

particles, in a reaction similar to that which occurs with the 

precious-metal catalyst. Viewed in another way, the presence of 

the catalyst merely speeds up a reaction which would occur anyway 

(although this can have a significant effect on human exposure to 

the reaction products). According to analysis by the California 

Air Resources Board staff (1984), roughly 1.53 lb of secondary 

particulate is formed per pound of SO emitted in the South Coast 

2 

Air Basin. For a diesel engine burning fuel of 0.29 weight 

percent sulfur at 0.42 lb of fuel per horsepower-hr, this is 

equivalent to 0.85 grams per horsepower-hour. For comparison, 

the average rate of primary or directly-emitted particulate 

emissions from heavy-duty diesel engines in use was about 0.8 

grams/BHP-hr in a recent study (EMA, 1985). 

Quite aside from its particulate-forming tendencies, sulfur 

dioxide is recognized as a hazardous pollutant in its own right. 

The health and welfare effects of SO emissions from diesel 

2 

vehicles are probably much greater than those of an equivalent 

quantity emitted from a utility stack or industrial boiler, since 

diesel exhaust is emitted close to ground level in the vicinity 

of roads, buildings, and other concentrations of people. 

3-4 
Engine durability effects 

Sulfur in diesel fuel has been recognized for many years as a 

major — and probably ite major — cause of wear in piston rings 

and cylinder liners (Blanc,1947; Furstoss, 1949). The rings and 

liners are generally the critical wearing parts in the diesel 

engine (Lilly, 1984), so that the rate of wear in these parts is 

directly related to the frequency of engine overhauls. 

The relationship between ring and liner wear and overhaul 

frequency is supported by the results of a survey comnissioned by 

the Engine Manufacturer's Association (Survey Data Research, 

1981). This study found that 80 percent of the fleets surveyed 

considered high oil consumption a primary indicator of the need 

to rebuild an engine, while 57 percent considered excessive 

blowby rates a primary indicator. Both of these indicators are 

directly related to ring and liner wear. Several other ccomon 

criteria for rebuilding — including reduction in oil pressure, 

major engine failures, and poor oil analysis results — are 

indirectly related to ring and liner wear. This is due to the 

effect of increased blowby in increasing the rate of acid 

deposition in the oil. 

Sulfur contributes to ring and liner wear through two mechanisms: 

corrosive wear and deposit formation. Corrosive wear occurs when 

the sulfur in the products of coabustion attacks and corrodes the 

3-5 
P.51 

piston rings, cylinder liners, and other exposed parts. This 

corroeion is most severe when liner temperatures are below the 

dewpoint of sulfuric acid in the exhaust gases. Operation below 

the acid dewpoint allows sulfuric acid to condense on the liner 

surface. This occurs during cold starting and warmup, and can 

also occur at light loads. Turbocharging (which raises the acid 

dewpoint) can exacerbate this problem (Lilly, 1984). Experiments 

with fuels of different sulfur levels have shown that corrosive 

wear also occurs (at a slower rate) even at normal operating 

temperatures. 

In addition to their corrosive attack on rings and liners, the 

sulfur compounds in the blowby gases can coonbine with and acidify 

the oil. If unchecked, this leads to rapid corrosion and wear of 

bearings, camshafts, and other lubricated parts. In order to 

keep these effects within bounds, all heavy-duty engine oils are 

now formulated with highly alkaline dispersant additives. These 

additives are typically based on metals such as calcium and 

barium, which conbine with and neutralize the acid. Without such 

additives, or where the additives have been depleted by combining 

with the acids in the blowby, corrosive wear rates with high 

sulfur fuel are very high (Dyson et alia, 1957); with them, wear 

rates can be kept within reasonable bounds. 

In addition to corrosive wear, ring scuffing and sticking and 

loss of oil control due to hard coky deposits on the piston are 

3-8 
P.52 

the other major sources of wear on piston rings and cylinder 

liners* Deposit formation at low and moderate temperatures is 

heavily affected by sulfur — low sulfur fuels result in fewer 

and lighter deposits (McGeehan et alia, 1983). At high 

temperatures, such as those in the top band of the piston, sulfur 

does not directly affect deposit formation. There is an indirect 

effect, however, since the alkaline additives in the engine oil 

are also responsible for the control of piston and other engine 

deposits, and their dispersant activity is lost as they are 

neutralized by combination with sulfur. 

The greater the concentration of alkaline additives in the oil, 

the greater the degree of protection against corrosive wear. The 

permissible additive concentration is limited by other 

considerations, however, to a maximum of about 6-10 Total Base 

Numbers or TBN (Gergel, 1980). One TEN is an alkali concentration 

equivalent to 1 mg of potassium hydroxide per gram of oil. The 

rate of neutralization of the alkaline additives is proportional 

to the rate of sulfur addition to the oil, which is proportional 

to the sulfur content of the fuel and the blowby rate. 

Presently, additive depletion is a limiting factor in the length 

of time permissible between oil changes (other limiting factors 

are soot accumlation, contamination with water or fuel, and 

oxidation of the oil). Greatly reducing sulfur might make it 

possible to extend oil change intervals significantly. 

3-7 
P.53 

Alternatively, or perhaps in addition, the amount of metallic 

additive in the oil could possibly be reduced. This would be 

desirable for trap-oxidizer equipped vehicles, since the 

noncombustible metal sulfate ash from the alkaline additives is 

collected by and eventually clogs ceramic monolith traps (Sachdev 

et alia, 1983; Hardenburg, 1985). 

Generally, the use of alkaline additives with adequate oil change 

frequency has resulted in acceptable wear rates and engine 

lifetimes with fuel of less than 0.5 percent sulfur by weight. 

However, despite the presence of alkaline additives, engine wear 

rates are greater with more sulfur in the fuel, and most 

observers agree that use of very low sulfur fuel would probably 

extend engine life. Because the wear rates in question are 

small, however, they have attracted little attention, and 

applicable recent data comparing the effects of moderate vs. 

very low sulfur levels in automotive engines are not available. 

There is abundant information concerning the effects of 

high-sulfur fuel in shortening engine life, but virtually no data 

on the effects of very low-sulfur fuel in lengthening it. 

Figure 3.1, taken from a study by Tennyson and Parker (1970), 

represents the best available information on the effects of very 

low sulfur fuels on relative wear rates. The figure shows the 

effects of fuel sulfur on piston ring wear rates in a two cycle 

locomotive engine as a function of the total base number (TBN) 

3-8 
P.54 

IRON FACE WEAR VERSUS FUEL SULFUR 

FRESH ANO USEO OILS 

Op«n Painlj • FretH Oils 

Clotad Pointt - used Oils 

0.2 a3 at a; at ar a: 

Fu*l Sulfur. Weiant Ptretnl 

L1AV 

1.0 

Figure 3.1: Effect of fuel sulfur content and oil alkalinity on piston ring 

tr rates in a locoeotive engine (Tennyson and Parker, 1970). 

3-9 
P.55 

remaining in the oil. 

The corrosive wear rates measured by Tennyson and Parker are 

probably lower than those which would be experienced in 

automotive engines, and thus the effects of differing sulfur 

levels are probably understated. The data were taken at high 

loads and in steady-state operation, and care was taken that the 

engine was not allowed to cool down in order to prevent possible 

condensation. High-load operation promotes abrasive wear, while 

condensation greatly increases corrosive effects. Thus, the 

curves in Figure 3.1 probably show the minimm effect of low 

sulfur fuel — that which would be observed in constant 

high-power operation. The difference in wear rates would 

probably be much higher during warm-up and light-load operation, 

where condensation can occur. 

Even given these limitations, it is instructive to consider the 

implications of Figure 3.1 for engine life estimates on 

low-sulfur fuel. The TBN of an oil declines in use, as the 

alkaline additives are depleted by combination with sulfur. An 

example of this is shown in Figure 3.2. For a typical heavy-duty 

oil with an initial TBN of 6 to 10, the average TBN over the 

period between oil changes is probably somewhere between 4 and 7, 

depending on the sulfur content of the fuel and the blowby rate 

of the engine. For this TBN, Figure 3.1 indicates that going 

from 0.3 percent sulfur to 0.05 percent would decrease wear rates 

3-10 
P.56 

19 

Figure 3.2: Loss of alkalinity in oi 

by sulfur (Sergei, 196*1). 

1 during use due to neutralization 

3-11 
by about 30-40 percent, while going from 0.3 percent to the 

maximum of 0.5 percent permitted by the ASTM standard would 

increase wear by about 40 percent. Extrapolating these 

differences over the whole life of the engine would result in an 

increase or decrease in engine life and mileage between major 

overhauls of up to 40 percent! 

It should be emphasized that these are probably mintmm 

differences — during warmup and low-load conditions the effect 

of sulfur levels is much greater. Figure 3.3, taken from a paper 

by Peugeot (1984), shows relative rates of ring wear during 

warm-up as a function of fuel sulfur. This plot shows roughly a 

65 percent reduction in wear in going from 0.3 percent to 0.05 

percent sulfur. Automotive diesel engines experience varying 

duty cycles, but many see a significant amount of cold operation, 

and wear during starting and warmup is disproportionately high. 

It should be noted that laboratory tests of wear rates, even 

relative wear rates, require corroboration by field experience 

before they can be considered reliable. Tb date, controlled 

tests of wear rates and engine life with low-sulfur diesel fuel 

do not appear to have been done, and the estimates given in the 

preceding paragraphs are thus somewhat speculative. Experience 

gained in the South Coast Air Basin, where low-sulfur fuel is now 

mandatory, may shed considerable light on in-use wear effects, 

but several more years of operation on that fuel will be 

3-12 
TEiVf^WIURE D'EAU KJTEUR 60' 

C00L0NG WATER AT 60°C 

P.58 

Taux d'usure de la segmentation 

(Base 1 pour 02 de soufrt) 

8 RATE OF WEAR OF RINGS % 

(BASE 1 FOR 0 2 SULPHUR) 

L7 

U 

L3 

0,25 Or* 

Z SULPHUR BY WEIGHT 

IN THE FUEL 

%dt soufre^nasse) 

urtenu dans le oase 

cys 

•» •». c**mr~± nf *UM1 sulfur content on piston ring wear rate 

Fl8U TM ?•?: !""!! °l^ l i^ In auto~tiv. diesel -ngin. (P«ugeot, 1984a, 

during engine Mareup in an autoeot 

S-13 , 
P.59 

required. 

In this context, it is instructive to consider the experience of 

gasoline engines with unleaded gasoline. Leaded gasoline 

contains bromine and chlorine additives as lead scavengers, while 

unleaded gasoline does not. These additives, like sulfur, are 

burned to form strong mineral acids in the blowby and exhaust. 

As discussed in Weaver (1984a), extensive in-use experience with 

unleaded gasoline has demonstrated a substantial decrease in 

engine wear rates compared as a result of eliminating these 

additives. A series of comparison tests in taxicabs, for 

instance, showed 70-300 percent greater wear in bearings and 

piston rings using leaded gasoline and a modern (universal type) 

oil. 

For comparison, the acid concentration in leaded gasoline at 3.0 

grams of lead per gal is about .015 moles of acid per gallon, 

while the acid concentration in diesel fuel at 0.3 percent sulfur 

is 0.3 moles per gallon — about 20 times as great. Presently, 

most heavy-duty diesel and spark ignition engines use oils 

formulated for both (universal oils). It is reasonable, 

therefore, to expect that the effects of a low sulfur fuel in 

reducing wear rates in diesels would at least be comparable to 

those of unleaded gasoline in spark ignition engines. 

Tb sum up, there is a consensus among knowledgeable parties that 

3-14 
wear would be reduced, probably significantly, with a change to 

low sulfur fuel. Quantitative data defining him ouch engine life 

will be extended are very scarce, and in-use data on this point 

are unavailable. The best indicator available is the locomotive 

study conducted by Tennyson and Parker (1970), which is probably 

somewhat conservative for estimating differential wear effects in 

automotive engines. Further research — including carefully 

controlled field tests — would be highly desirable. 

3 . 2 ABTMA.TIC OTWTFNT AND ICNTTICN QDALITY 

The volume fraction of aromatic hydrocarbons in the fuel, or 

aromatic content, has important effects on emissions, noise, and 

performance in diesel engines, and an indirect effect on fuel 

economy. The emissions and performance/fuel economy effects are 

discussed separately below. 

Rntuioni ftffflcti 

The emissions effects of aromatics are due to at least two and 

possibly three causes. The first reason is the close correlation 

between aromatic content and ignition quality, as measured by the 

cetane nunber. As discussed in the last chapter, this is 

especially important for cold start and light-load operation, but 

it affects particulate, noise, and hydrocarbon emissions even in 

3-15 
P.61 

normal operation. 

The second effect is due to the fact that aromatic hydrocarbons 

are denser than paraffins or napthenes. As a result, highly 

aromatic fuels are denser than less aromatic ones, so that (since 

fuel injection systems meter by volume) a greater mass of fuel 

can be injected into the cylinder. This increases the power 

output of the engine slightly, but can also raise the fueling 

rate above the smoke limit — resulting in disproportionately 

greater smoke and particulate emissions. 

A third, possible effect on emissions may result from the greater 

soot-forming properties of aromatics. The aromatics' propensity 

to form soot in steady-state coabustion is well known. It can be 

explained by the fact that the aromatic ring decomposes readily 

to acetylene, while soot is known to be formed by a rapid 

polymerization of acetylene. The relative importance of this 

effect in diesel engine emissions is not known, however. 

The effeets of aromatic hydrocarbons on ignition quality and 

density are not unique. Napthenes are also denser and have lower 

ignition quality than do paraffins, although the differences in 

each case are much less than for aromatics* It is conceivable, 

therefore, that some weighted index of aromatic and napthenic 

qualities might be a better predictor of emissions effects than 

aromatics alone. One index which has this character already is 
the aniline-point, which also has the advantage of being simple 

and widely used. The data available are mostly expressed in 

terms of the aromatic content, however, and that is the index 

which will be discussed here. 

The effects of aromatic content on emissions appear to be 

different for light-duty IDI and heavy-duty DI engines. 

Emissions levels in IDI engines appear to be fairly sensitive to 

ignition quality, as measured by the cetane number. This may be 

due to differences in the effect of cetane number on ignition 

delay. In naturally aspirated IDI engine, Olree and Lenane 

(1984) found a good correlation between measured ignition delay 

and cetane number for a variety of operating conditions, while 

Barry and coworkers (1985) found no correlation between the two 

in a highly turbocharged, intercooled heavy-duty engine. It 

appears that, for heavy-duty engines, cetane is mostly important 

for cold starting, and does not greatly affect warmed-up 

emissions levels as long as the ignition quality is sufficient to 

allow normal combustion. 

Measurements of aromatic content effects on emissions also appear 

to be sensitive to the testing conditions used, and to the 

specific engine model being tested. For instance, in a series of 

light-duty tests conducted for the Coordinating Research Council 

(Hare, 1985), workers at Southwest Research found a significant 

correlation between aromatic content and particulate emissions 
P.63 

for each of-four light-duty automobiles. The magnitude of the 

regression coefficient relating the two, however, varied by a 

factor of more than eight from one engine to another. Major 

differences were also found between the effects measured on the 

Federal Test Procedure cycle and those measured at 30 and 56 MPH 

cruise conditions. Bergin (1983) also found large differences in 

the effects of aromatics as a function of engine load. 

The dependence of aromatic effects on the specific test cycle 

also appears in heavy-duty engines. Barry et alia (1985) found 

major differences in aromatic effects in a modern heavy-duty 

engine between the Federal Heavy-Duty Transient test cycle and 

the earlier 13-mode test* The engine used was a Caterpillar 

3406B turbocharged and aftercooled line-haul truck engine, and 

had been calibrated for a low NOx emission rate of 6.5 g/EHP-hr. 

The fuels used were specially compounded so that they had similar 

back-end volatility and sulfur content, and the fuel pump was 

adjusted to compensate for variations in fuel density. Thus, the 

only major emissions-related parameter being varied was the 

aromatic content. 

Figure 3.4 compares the test results obtained by Barry and 

co-workers with a nunber of fuels with differing aromatic 

contents. Data were obtained on both the EPA transient and the 

13-mode cycle. As the figure indicates, both sets of data lie 

along reasonably straight lines, but the slopes of the two 
AROMAHC CONTENT EFTCCT 

ON WSRnCULAIES 

P.64 

I I I 

AfttMMC CONTENT. VOL %. 

Figure 3.4: Effects of fuel aroeatic content on particulate eaissions: 

steady state vs. transient tests on a heavy-duty engine 

(Barry et alia, 1983). 

3-19 
regression lines differ by a factor of about ten. 

Two inportantjeonclusions can be drawn from the data in Figure 

3.4. First, the aromatic content of the fuel has a significant 

effect on particulate emissions as measured in the Federal 

transient test. Second, data taken on the 13-mode steady-state 

test cycle (and presumably other steady-state cycles) cannot be 

used to predict fuel effects on the transient test. The same is 

also true of extrapolation from the 13-mode test to in-use 

emissions. The transient test cycle was designed to be 

representative of conditions in actual use, while the 13-mode and 

other steady-state cycles do not represent in-use operation very 

well. Thus, any extrapolation of laboratory test results to 

in-use emissions should be done using transient-cycle data. 

The restriction to using only transient cycle data to predict 

in-use emission effects is inconvenient, since such data are 

extremely rare. The transient cycle is still fairly new, and 

engine test cells capable of running it have mostly been 

dedicated full-time to development work for the 1988 NOx and 

particulate emissions standards. Work to examine the relative 

effects of fuels on emissions has had much lower priority, and 

generally has not been done. 

A comprehensive study — funded by the Coordinating Research 

Council — to examine fuel effects on a nunber of heavy-duty 

3-20 
P.66 

engines is now underway at Southwest Research Institute, but the 

data from this study will not be available for at least two 

years. In the meantime, only four studies examining fuel effects 

in heavy-duty engines are available in the literature. Of these, 

two deal with the effects of synthetic fuels (Ullman and Hare, 

1983; Ullman et alia, 1984). This introduces the potential for 

confounding effects due to other changes. The partial results of 

a third study are reported by Wall and Hoekman (1984), but the 

authors did not report numerical data for the transient test. 

Wall and Hoekman reported only the fact that "statistically 

significant" relationships between aromatic content and 

particulates and between sulfur content and particulates (but not 

between back-end volatility and particulates) were found. 

The fourth study showing fuel effects on emissions in the 

transient test is that of Barry and co-workers, which has already 

been cited above. This study was specifically designed to 

examine the effects of sulfur, aromatic content, and back-end 

volatility on emissions. Tests were run on a set of fuels which 

were specially compounded to vary only one of these indices at a 

time. As a result, the test data can be interpreted clearly and 

unambiguously as showing a strong effect of aromatic content on 

particulate emissions. At a fuel sulfur level of 0.25 percent, 

the relationship between aromatic content and particulate 

emissions for the Caterpillar 3406B engine tested was roughly 

3-21 
P.67 

Particulate = 0.143 + A • 0.0113 (3.1) 

where particulate is in grams per EHP-hr and A is the aromatic 

content of the fuel in percent. However, about 0.033 g-EHP/hr of 

sulfate were included in the particulates in each test (this low 

level was due to storing the filters over a dessicant to remove 

the bound water). Subtracting this value from the constant term 

in equation 3.1 gives 

Carbonaceous Particulate = 0.120 + A • 0.0113 (3.2) 

where the units are the same as for equation 3.1. "Carbonaceous 

particulate" is defined to include both the sooty fraction and 

the soluble organic portion of the particulate material, but not .... _ 

the inorganic sulfates. Since variations in aromatic content 

could only affect emissions of carbonaceous particulate, this is 

the appropriate variable to consider. 

Equation 3.2 is valid only for a single engine, and is based on 

only a single series of tests. However, it agrees moderately 

well with one of the synthetic fuel studies reported by Ullman 

and co-workers, and with the finding by Wall and Hoekman that 

aromatics had a statistically significant effect on particulate 

emissions. The other synthetic fuel study showed little or no 

effect of aromatics on particulates, but this may have been 

3-22 
P.68 

confounded by changes in the other hydrocarbon components of the 

fuels. 

A great many studies of fuel effects on light-duty diesel 

emissions have been reported in the literature. Bykowski and 

co-workers (1983) have sunmarized and combined the data from a 

nunber of these studies. Most of these studies have agreed in 

finding that aromatic content and back-end boiling point are the 

important variables affecting emissions. Unfortunately, none of 

these studies examined fuel sulfur as an independent variable, 

nor did Bykowski et alia reanalyze for sulfur effects. Since 

sulfur content is now known to have a strong effect on 

particulate emissions, this casts serious doubt on the validity 

of the correlations developed. 

In addition to possible confounding of aromatic and sulfur 

effects, it appears that the effects of aromatic content on 

light-duty particulate emissions vary greatly from engine to 

engine. Figure 3.5, taken frcm Bykowski et alia, shows the 

regression lines relating aromatics to particulate emissions 

calculated for each of a nunber of different studies. As the 

figure shows, these studies do not all agree even on the sign of 

the effect, much less on its magnitude. 

From the data at hand, it is impossible to give a reliable 

quantitative estimate of the change in light-duty diesel 

3-23 
P.69 

3.2 

2.8 • 

0 *•« • 

R 

M 

P 2.0 • 

A 

R 

T 

•.6 

• .2 • 

.80 

.40 *"* 

X 

0.0 • 

.•. 

0. 

.•.. 

to 

.•.. 

13 

.•.. 

20 

.•.. 

23 

.•....•....•.. 

33 

30 40 

AMOMATIC , /, 

.•.. 

43 

.•.. 

30 

.•.. 

33 

.•.. 

63 

60 

.•. 

70 

Figure 3.S: Regressions of particulate eaissions vs. fuel aroeatic content 

froa a nuaber of studies using different light-duty engines 

(Bykowski et alia, 1983). 

3-24 
P.70 

emissions that would result from a change in aromatic content. 

As an order-of-magnitude estimate, the regression line for all 

petroleum-derived fuels calculated by Bykoswki, et alia may be 

representative. This regression is shown in Figure 3.6. It gives 

the normalized particulate index as 

I = 0.635 + 0.01269 * A (3.3) 

where I is the ratio of particulate emissions with the test fuel 

to those using a standard reference fuel, and A is the volume 

fraction of aromatic hydrocarbons. 

Effect* on fuel economy, performance and diirnMHty 

As noted in Chapter Two, the aromatic content is closely 

correlated with cetane nunber. Cetane nunbers are important for 

cold starting of both direct injection (DI) and indirect 

injection (IDI) engines. They are especially important for DI 

engines, since the universal use of glow plugs on IDI engines 

makes them less susceptible to starting problems. Daimler-Benz 

(1984) has stated that 45 cetane is the minimum allowable for 

cold starting, while numbers above 50 are much preferred. By 

this criterion, almost all U.S. diesel fuels would be marginal at 

best, while a large fraction would give unsatisfactory 

performance. 

3-25 
s.2 • ; 

2.e • ; 

N 

0 '. 

R 2.« • ; 

M * 

P 2. 0 * 

A . 

R 

T 

1.6 • 

1.2 • A AA A 

A A A 

AA AA A 8 A 

. AT" A A AA A^-*Ol " 

.A A A A AA 4—***T* ^ A 

. 8 0 • A * - **—*^" ^ V-A'a ; 

XA-KJTA A A AA> 

.A A A >" A 

.A >»"^ A A 

. 4 0 *A >* 

X ^A 

m» 

m* . 

m* 

A - ' 

* • -" ' ^-—— \ 

A A

 ^ " ^-—""" A 

AAA *, ' ^.^J*—-" ^ • 

l - 4 ^ —^^ 

A AA8B X -TAR T -1. 0 

AA A A 

A • 

A 

• ^ 

3. IS 23 33 45 JJ 6S 

0 . 10 20 30 40 SO 60 70 

AROMATIC, X 

Figure 3.6: Regression of particulat e eaissions vs. fuel aroeatic content: 

coabined data froa a nuaber of light-duty engine studies 

(Bykowski et alia, 1983). 

3-26 

P.71 

i 
P.72 

Reducing the aromatic content of diesel fuel may slightly reduce 

fuel economy and maximum power in existing engines. This is due 

to the fact that a less aromatic fuel contains slightly less 

energy per unit of volume. In new engines, however, this effect 

would be more than offset by the reduction in compression ratio 

made possible by higher cetane nunbers. Presently, heavy-duty DI 

engines are required to have higher compression ratios than would 

be optimal for fuel economy in order to ensure satisfactory cold 

starting. If a higher cetane level were guaranteed, 

manufacturers could decrease compression ratios slightly, with 

significant benefits in fuel economy and (possibly) emissions. 

A recent report by workers at Cummins gives some idea of the 

magnitude of the effects involved. Phatak and Nakamura (1983) 

experimented with compression ratios of 14:1, 16:1, and 18:1 in a 

naturally aspirated DI diesel. They found that power and fuel 

economy were best, and smoke was lowest, at 14:1, next best at 

16:1, and worst at 18:1. Figure 3.7 shows some of these results. 

The brake-specific fuel consumption at 14:1 was about 10-15 

percent lower than at 18:1 in these tests. At 14:1, however, the 

engine could not be started even at 32 F, while at 16:1 it took 

90 seconds to start at 32 F and would not start at all at 14 F. 

At 18:1 the engine started satisfactorily at temperatures as low 

as -4 F. The cetane nunber of the fuel used was not given, but 

was probably in the range of 42 to 45 which is typical of diesel 

3-27 
P.73 

75 r 

oe 

I 

ai. 

x 

.63 

a .57 

vt 

09 

.51 

.45 

COMPRESSION RATIO 

_l_ J_ J_ _L 

1000 1200 

1400 1600 1800 2000 2200 2400 

SPEEO (RPM) 

> 

S 4 

< 

O 

o 

s 

6.00 r 

5.20 -

.40 -

3.60 

2.80 

2.00 

1000 1200 1400 1600 1800 2000 2200 2400 

SPKOtRPMl 

Figure 3.7: Effect of changes in coapression ratio on fuel consueption and 

»ke (Phatak and Nakaaura, 1984). 

3-28 
P.74 

#2. 

Much of the noise produced by a diesel engine, especially at 

light loads, is due to the rapid pressure rise which results from 

premixed burning due to the ignition delay. A lower-aromatic 

fuel would reduce this noise by reducing the ignition delay, 

while a highly aromatic fuel would increase it. A fuel with 

sufficiently poor ignition quality could even affect the 

durability of the engine, due to the high transient pressures 

resulting from the long ignition delay period. This is not a 

significant problem at present, except for marginal fuels, but 

could conceivably become a problem if fuel quality continues to 

decline. 

3.3 PUEL BOILING RANCS AMD tt»ATIL ITY 

Many discussions of fuel effects on particulate emissions have 

concentrated on the 90 percent point, end point, or other 

indicators of back-end volatility. A nunber of studies have 

indicated significant correlations between back-end volatility 

and particulate emissions in light duty vehicles (e.g. Burley and 

Rosebrock, 1979} Hare and Baines, 1979). Researchers at Chevron, 

however, have shown that these results may have been confounded 

with the effects of sulfur, which is strongly correlated with 

back-end volatility in petroleum-derived fuels (Chevron, 1984). 

3-29 
Bykowski and co-workers (1983) combined the results of 11 studies 

of fuel effects on emissions in light-duty vehicles. Figure 3.8 

is a plot of normalized particulate emissions versus fuel 

90-percent point for the combined data, along with the best-fit 

lines calculated for petroleum-derived fuels (solid line) and 

alternative fuels (dashed line). As the figure shows, these data 

are highly scattered, and neither regression equation predicts 

very well. In addition, the fact that the slope of the 

regression line for alternative fuels is nearly zero (and 

negative) while that for petroleum-derived fuels is larger and 

positive strongly suggests that the results are being confounded 

by some other variable, such as sulfur content. 

Bergin (1983) used a variety of low-sulfur fuels to examine the 

effects of aromatic content and 90 percent point on light-duty 

emissions as functions of engine load. He found that 90 percent 

point accounted for about half the variation in particulate 

emissions at light loads, with aromatics accounting for the other 

half. At higher loads, where particulate emission rates are 

greater, 90 percent point had little effect, and at the highest 

loads, a higher 90 percent point was actually correlated with 

lower particulate emissions. 

Comparatively little work has been done comparing heavy-duty 

engine emissions on different fuels using the heavy-duty 

3-30 
P.76 

J.2 

2.8 

N 

0 2.4 

R 

M 

f 2.0 

A 

R 

T 

1.6 

'.2 

.80 

.40 

.••.•••••..•. 

i.*....*....*....*....*...**....*....*....*....*....*....*....*....*, . 

75. 125 115 225 275 325 375 

100 IJO 200 250 300 330 400 

8PNINETY, °C 

Figure 3.8: Regression of particulate eaissions vs. fuel 9*J percent point: 

coabined data froa a nuaber of light-duty engine studies 

(Bykowski et alia, 1983). 

3-31 
P.77 

transient test. As discussed in Section 3.2, fuel-effects 

results obtained at steady state appear to differ significantly 

from those obtained on the transient test. Two recent studies 

which included both types of tests were conducted by Chevron 

Research (Chevron, 1984; Wall and Hoekman, 1984), and the work of 

Barry et al (1985). The Chevron study showed a slight positive 

effect of 90 percent point on particulates in steady-state 

operation, while Barry and co-workers showed a slight negative 

effect. More importantly, neither study showed any statistically 

significant effects in the transient test. The data of Barry et 

alia are reproduced in Figure 3.9 . 

Frcm these data, it appears that changes in back-end volatility 

per s£ have little effect on particulate emissions from 

heavy-duty DI engines, and only a minor effect on those from 

light-duty IDI engines. Increases in back-end volatility in 

conmercial diesel fuels will be limited by the ASTM specification 

for diesel #2, and by the need to maintain acceptable cold-flow 

performance. Significantly decreasing back-end volatility would 

be very expensive, and would make achievement of other 

fuel-quality goals more difficult. For these reasons, 

consideration of an emissions-related standard for back-end 

volatility in diesel fuels appears to have little justification 

at this time. 

3-32 
P.78 

Stil l under development 

« - " «rnuL-.=riru»,^^ 

3-33 
P.79 

3.4 DENSITY AND VISCOSITY 

Fuel density has an important effect on fuel economy and on 

particulate emissions. The energy content of a given mass of 

diesel fuel is (roughly) constant, which means that a denser fuel 

(containing more mass per unit of volune) will result in a lower 

volumetric fuel consumption. Since fuel is metered and sold by 

volume, not mass, this can affect the economics of fuel use. 

The effects of density on particulate emissions derive from the 

same cause. The power output of a diesel engine is determined by 

the amount of fuel injected into the cylinder to burn. Beyond 

some point (known as the smoke limit), smoke and particulate 

emissions increase very rapidly as the amount of fuel injected 

increases. Fbr this reason, diesel fuel injection pumps are set 

to limit the maximum volume of fuel injected to a value near to 

the smoke limit. An increase in density, however, means that a 

greater mass of fuel is contained in this maximum volune. This 

can result in a small increase in power, accompanied by a large 

(and disproportionate) increase in smoke and particulate 

emissions. 

Fuel viscosity is also important to fuel economy and emissions 

performance. In modern DI engines, a great deal of development 

effort has been expended on optimizing the combination of fuel 

spray characteristics, airflow patterns, and injection timing in 

3-34 
P.80 

order to obtain the best tradeoff between emissions, fuel 

economy, driveability, and other factors. Fuel viscosity changes 

can significantly affect fuel spray characteristics, and thus 

degrade the coitustion process. Tbo high a viscosity also 

increases the forces on the fuel injection pump, while too low a 

viscosity may affect the lubrication of the pump. Either change 

may result in excessive wear on the fuel injection system. 

It is important to note that the absolute values of the density 

and viscosity are not especially important — engine designs can 

be optimized for any reasonable values of these parameters. What 

is important is that the variation in density and viscosity 

values be minimized, so that engines optimized for one set of 

values are not faced with a fuel having a radically different 

set. 

As discussed in Section 2.3, density and viscosity are determined 

by the hydrocarbon composition of the fuel. Thus, regulatory 

changes which tended to standardize hydrocarbon content (e.g. by 

limiting aromatics) are likely to reduce the variation in these 

properties as well. The issue of whether further standardization 

of these properties would sufficiently reduce emissions to be 

worth the cost is a difficult one, and beyond the scope of the 

present effort. It is recomnended that this question be 

considered as part of a more detailed study of potential fuel 

regulations. 

3-35 
P.81 

3.5 STABILITY, TIOTTT TTRHATION. AND OTHFR PHTPraTTFS 

The oxidation stability and deposit-forming qualities of diesel 

fuel affect both the long-term emissions and the long-term 

performance of the engines using it. Fuel oxidation in storage 

leads to plugging of fuel filters, and can damage the fuel 

injection system. Formation of excessive deposits on fuel 

injectors can affect fuel spray and injection timing 

characteristics, degrading both emissions and performance. 

Diesel fuels containing a large percentage of catalytically 

cracked stocks are generally considered to have poorer stability 

and greater deposity forming characteristics than straight-run 

diesels, and the increasing use of cracked stocks worldwide has 

created concerns in this area. 

Both oxidation stability and deposit-forming characteristics can 

be effectively controlled by the use of additives, and 

stability-enhancing additives are routinely used by many U.S. 

refiners. Additives to control deposit formation are more 

expensive, and are not widely used. As a result, some diesel 

engines (especially European and light-duty engines) have 

suffered from emissions and performance problems due to injector 

deposits. Several European manufacturers have advocated greater 

use of these additives in order to control these problems 

3-36 
P.82 

(Hardenburg, 1985; Lucki, 1984). Since these problems are linked 

to other indices of diesel fuel quality (such as cetane and 

arcmaUc content), it appears likely that a general inprovement 

in those characteristics would alleviate these problems as well. 

3-37 
P.83 

4.0 : MTTEUNG THE COSTS QF REFINING CHANCES 

The approach used to determine the costs resulting from changes 

in diesel fuel specifications was to develop a model of annual 

U.S. refining operations and to simulate operations at various 

levels of diesel fuel specifications. The refinery model 

determined the change in overall refinery margin (i.e. refined 

product revenues less raw material and operating costs) 

associated with restrictions in diesel fuel quality 

specifications. The analysis focused on the domestic refining 

industry and refined product demand projected for the year 1987. 

This section provides a description of the refinery model and theapproach used to develop the refinery cost estimates. The first 

three sections describe the model, its application to the 

analysis, and the modeling assumptions. A final section 

discusses limitations of the analysis. 

4 . 1 PV7WMV7BY MTFf. 

The model used for the refinery cost analysis was a version of 

the Depart- ment of Energy's Refinery Evaluation Modeling System 

4-1 
P.84 

(REMS). The Refinery Evaluation Modeling System (REIVE) is a 

modeling system used by the Department of Energy (DOE) to analyze 

U.S. petroleum supply issues and to provide input into other 

energy models. 

RIMS consists of two parts: a series of refinery IP models which 

simulate geographic refinery operations, and a transportation 

aggregator which simulates crude and product movement throughout 

the United States. The refinery model was designed to run 

separately in order to generate extreme point vectors for the 

refinery sector of the transportation model. It is the refinery 

model that was used to develop estimates of refining costs 

associated with diesel specification changes. 

The refinery model is a single-time period LP representation of 

crude and downstream processing and final product blending. "Tt'~-

is similar to those typically employed by refiners for planning 

and scheduling but in seme respects simplified. It has proven to 

provide a good representation of aggregate regional operations of 

U.S. refiners and has successfully undergone a nunber of 

validation/verification tests. 

The model "begins" with a representation of crude oil 

distillation through a series of crude assays. For each of about 

100 crude oils, the assays describe the yield of intermediate or 

final refined products generated during the initial distillation 

4-2 
P.85 

and their quality. Downstream from the crude distillation unit, 

the model contains comprehensive representations of all major 

refinery units. The downstream unit representations contain 

yield and cost correlations for various types and quality 

feedstocks as well as correlations used to determine output 

quality. 

The refinery model is capable of producing approximately 25 

products in its current configuration, roughly corresponding to 

the product categories as reported by COE. Major products, such 

as gasoline, jet fuels, middle distillates, and residual fuel, 

are blended to specific user-specified quality parameters. Other 

smaller volume products are recipe blended. 

The model determines an optimum solution to a specified objective 

(such as profit maximization) based on prevailing economic --. --. 

conditions and as limited by capacity constraints, product 

specifications or other user-specified con- straints. In 

addition to the optimum answer, the model provides economic and 

processing information on all aspects of the refining industry's 

operations, such as process utilizations or the rate at which 

costs change as operations are altered. 

The refinery yield model was originally developed in 1976, at 

which time it was used to support analysis related to the 

Strategic Petroleum Reserve. It since has been used by DOE and 

4-3 
EPA for several purposes. EPA has used the model to predict the 

costs of lead phasedown during the 1982 and 1984 rule- makings. 

4.2 Wm__AWm_Qi 

For this analysis, two regional models were developed to 

represent eastern U.S. (PAEDs I through IV) and western U.S. 

(PADD V) . The existing petroleum distribution network allows 

refiners to somewhat optimize aggregate operations through 

product exchanges, crude variations, etc., in each of these 

regions. However, there is very little connection between the 

West Coast and the remainder of the U.S. distribution system; 

hence, the two operate independently. 

For each region, projections were made of refinery supply and 

demand petroleum prices, product qualities and processing 

capacities for the year 1987. The industry was limited to 

processing facilities currently in place or projected to be 

completed by 1987; new investments beyond these were not assumed 

to be available within this timeframe. Each model was run with 

product demands fixed, except for liquid petroleum gas, coke, 

sulfur and residual fuel. Most inputs were also fixed, but the 

models were allowed to vary a marginal crude, butane and utility 

purchases. These initial runs defined a "base case" fore- cast 

of industry operation in each region with diesel fuel quality 

4-4 
P.87 

conforming to current specifications. 

After establishing the base cases, the models were again run with 

the same raw material, product, and pricing assumptions, but with 

more restrictive diesel fuel specifications a Because all other 

parameters were held constant between cases, the cost associated 

with changes in diesel specifications could be computed as the 

sum of changes in crude oil, butane and utility purchases; IfG, 

coke, sulfur, and residual fuel revenues; and other marginal 

operating costs (catalysts, chemicals, etc.). Fixed costs and 

capital charges were not included in the cost computations. 

These latter costs are already "sunk" and will not vary with 

diesel fuel specifications. 

The more restrictive diesel fuel specification cases first 

considered a reduction in sulfur content from current levels to 

0.05 weight percent. Then, with the sulfur content maintained at 

0.05 weight percent, diesel fuel aromatics content was lowered to 

17 volune percent. 

4.3 MTH . xggwsmrMS 

Refined product demand for 1987 was based on DOE's Annual Energy 

4-5 
P.88 

Outlook (EIA, 1985) and gasoline demands projected by EPA for 

their lead phasedown cost benefit analysis (Schwartz et alia, 

1984). Table 4.1 sunmarizes the projected demands used for the 

analysis. 

Product demands were disaggregated into PAEDs I-IV and PADD V 

based on historic market shares. Gasoline, nunber two heating 

oil, and diesel fuel demands were then adjusted to account for 

imports, arriving at the projected demand on refineries shown in 

Table 4.2. Gasoline and distillate imports were assumed to 

decline frcm current high levels due to growth in world petroleum 

demand and a decline in the worldwide refining capacity surplus. 

A diesel fuel demand of 1.25 million barrels per day (42.8 

percent of middle distillate demand) was estimated based on DOE*?-, 

projection of transportation distillate fuel. The same diesel 

fuel percentage was applied to both regions simulated. For PAED 

V, diesel fuel demand in the Los Angeles area was assumed to 

account for 26.5 percent of the regions demand. 

(Viiai* «nri rtthef Raw Material Supply 

A forecast of crude supplies for each region was based on the DOE 

Annual Energy Outlook, the HSMS model update, and current trends 

of imported crude oil. Supplies of unfinished oil feedstocks 

were also estimated based on historic trends. Refinery inputs 

4-6 
Table 4.1: U.S. Refinery Product Demand: 1987 (Thousand Barrels Per Day). 

Product Demand 

Unleaded Regular Gasoline 3,635 

Unleaded Premium Gasoline 1,210 

Leaded Gasoline 1,665 

Aromatics 130 

Naphthas 140 

Naphtha Jet Fuel 245 

Kerosene Jet Fuel 985 

Kerosene 110 

Diesel Fuel 1,250 

Other Distillate 1,670 

Residual Fuel (1) 1,420 

Lubes and Wax 185 

Asphalt and Road Oil 440 

Other (2) 3,075 

(1) Residual fuel varies in PAID scenarios. 

(2) Other includes aviation gas, gas oil to petrochemicals, still gas tope trochemi cals, ethane, propylene to petrochemicals, propane to 

petrochemicals, butylene to petrochemicals, coke, sulfur, process gas, 

normal butane, and LPG some of which are allowed to vary 

in PAH) scenarios. 

4-7 
P.90 

Table 4.2: Projected demand from refineries: 1987 (thousand barrels per day) 

Product 

Unleaded Regular Gasoline 

Unleaded Premiun Gasoline 

Leaded Gasoline 

Aromatics 

Naphthas 

Naphtha Jet Fuel 

Kerosene Jet Fuel 

Kerosene 

Diesel Fuel 

Other Distillate 

Residual Fuel 

Lubes and Wax 

Asphalt and Road Oil 

Other 

Demand 

PACK I-IV PACDV 

2,970 

1,000 

1,330 

130 

130 

180 

715 

100 

1,040 

1,390 

open 

170 

370 

open 

590 

200 

270 

1 

10 

65 

270 

10 

165 

220 

open 

15 

70 

open 

4-8 
P.91 

Table 4.3: Refinery inputs: 1987 (thousand barrels per day). 

Crude Oil 

High Sulfur 

Low-Sulfur High Aromatics 

Low-Sulfur Low Aromatics 

Marginal Mexican Isthmus 

Marginal Alaskan North Slope 

Unfinished Oils 

Natural Gasoline/Condensate 

Butane 

Alcohols/MIBE 

PACES I-IV pAJD Y 

4,100 

4,200 

800 

Varies 

0 

205 

195 

Varies* 

45 

1,620 

0 

215 

0 

Varies 

0 

10 

Varies* 

0 

* Limited to maximum of 1984 volumes. 

4-9 
are sunmarized in Table 4.3. 

In each region, available crude oils were aggregated into four 

crude mix pools: high sulfur crudes, low sulfur high aromatics, 

low sulfur low aromatics, and the marginal crude. In PAEDs I-IV 

the marginal crude was assuned to be Mexican Isthmus and in PADD 

V, Alaskan North Slope. 

Bew Material and Refined Product PHeea 

In the analysis, the cost of more restrictive diesel fuel 

specifications is determined by marginal crude oil and other raw 

material costs, marginal product revenues and miscellaneous 

operating costs. Refinery costs determined by the model are 

therefore a function of prices specified for marginal raw 

materials and products. These prices were assuned to remain 

roughly at current levels in real terms as shown in Table 4.4. 

Refined Product Speeifieatlong 

Refined product specifications for major refined products are 

shown in Table 4.5. Gasoline specifications and jet fuel, 

distillate, and residual fuel sulfur specifications were based on 

estimates of current quality. Other specification parameters 

were based on ASTM specifications. 

4-10 
P.93 

Table 4.4: Raw Material and Refined Product Prices: 1987 (Dollars Per Barrel) 

Raw Material PriTM */mr. 

Marginal Mexican Isthmus Crude $29.46 

Marginal Alaskan North Slope Crude 28.75 

Isobutane 23.23 

Normal Butane 22.20 

Products 

LPG 18.44 

Lew-Sulfur Resid (PAEDs I-IV) 27.50 

Low-Sulfur Resid (PAID V) 27.80 

High-Sulfur Resid (PADDs I-IV) 26.20 

High-Sulfur Resid (PAID V) 26.20 

Sulfur 50.00 

High-Sulfur Coke 15.00 

4-11 
P.94 

Table 4.5: Refined Product Specifications 

Gasolines 

PAID I-IV Uni. Reg. 

Uni. Prm. 

Leaded 

Padd V Uni. Reg. 

Uni. Prm. 

Leaded 

Kerojet Fuel 

All Regions 

Distillates and Resid 

PADD I-IV Diesel 

No 2 Fuel 

L.S. Resid 

H.S. Resid 

PADD V Diesel 

Nb 2 Fuel 

L.S. Resid 

H.S. Resid 

Octane 

HCN W U R4M/2 

91.7 83.0 87.4 

96.4 86.8 91.6 

92.9 85.3 89.1 

92.5 83.4 88.0 

96.5 86.7 91.6 

93.4 85.1 89.3 

Sulfur API Gravity 

RVP 

psi 

12.0 

12.0 

11.9 

10.5 

10.7 

10.5 

Lead 

ffPff 

— 

0.1 

~ 

~ 

0.1 

Lum. Nb. 

max. min. max. 

.1 39. 51. 

Sulfur API Grav. 

min 

0.28 30 

0.28 30 

0.40 

2.50 

0.30 30 

0.24 30 

0.40 

2.50 

Flash 

min. 

125 

125 

150 

150 

125 

125 

150 

150 

mioa 

45 

Min. 

440 

10 

10 

10 

10 

Max % Evap 

at 212 F 

60 

60 

60 

60 

60 

60 

% Evap 

640 

90 

90 

90 

90 

Viscos 

min. 

1.9 

1.9 

1.9 

1.9 

ity 

mn*. 

4.1 

4.1 

2S0~ 

300 

4.1 

4.1 

300 

300 

4-12 
P.95 

Current Number 2 heating oil and diesel fuel sulfur levels on 

average are below levels specified by ASTM or Federal and state 

environnental regulations. This is due to a nunber of factors 

such as the availability of very low sulfur stocks in certain 

refining areas, the use of desulfurization processing for 

purposes other than meeting sulfur standards (i.e., 

stabilization, mercaptan reduction, etc.), products distribution 

constraints, etc. In this analysis, it was assuned that'these 

factors impose an "artificial" limit on the sulfur content of 

distillate fuels. Therefore, current Number 2 sulfur levels were 

maintained as diesel fuel sulfur levels were further 

constrained. The Niniber 2 heating oil pool was not allowed to 

serve as a "sink" for sulfur removed from the diesel fuel pool. 

Refinery capacities were limited to those facilities in place as 

of January 1, 1985, and announced expansions scheduled for 

completion by 1987. Refinery processing capacity assumptions are 

sunnarized in Table 4.6. , 

4.4 Mm , Attn TWTA LIMITATTflC 

Both the modeling approach and the data used to support model 

assumptions for this analysis are to some extent limited. The 

4-13 
Table 4.6: U.S. refinery processing capacities: 1987 (thousand barrels per day) 

Process PAffig 1'IY PAID y 

Crude Distillation 12,270 2,949 

Vacuum Distillation 5,334 1,552 

Coker-Delayed 848 377 

Coker-Fluid 116 87 

Visbreaker 157 75 

Naphtha Hydrotreater 3,266 656 

Distillate HDS 2,289 343 

FGC Feed Hydrofiner 1,093 394 

Resid Desulfurizer 316 24 

Cat Reformer 150 PSI 1,038 61 

Cat Reformer 350 PSI 141 539 

Cat Reformer 450 PSI 588 41 

Fluid Cat Cracker 4,526 685 

Hydrocracker 649 410 

Alkylation Plant 812 146 

Cat Polymerization 85 6.8 

Pen/Hex Poymer ization 189 0 

Butane Isomerization 59 17 

4-14 
use of a linear programing representation of aggregate regional 

refining operations results in "over- optimization" which cannot 

be achieved in reality. The refining industry has historically 

operated somewhat as an integrated system and demonstrated its 

ability to efficiently utilize available raw materials and 

processing capacity through exchanges and changes in feedstock 

qualities, etc. However, the extent of system optimization 

achieved by the model overstates actual capabilities. 

Some model optimization is negated by analyzing differences in 

two optim- ized solutions. Optimization occurs in both the base 

case and the more restric- tive specification cases. Differences 

in costs are only affected if the over- optimistic assumptions 

generate greater savings in one case than in the other, and the. 

size of error is only the difference in overoptimization. For 

this reason, the operating cost estimates for reducing diesel 

specifications may be reasonable. 

One model overoptimization which is not negated by examining 

differences in overoptimized solutions is in the area of process 

utilization. The model optimally allocates various quality 

refinery streams in order to minimize the cost of processing. As 

a result, the model tends to underestimate the level of 

processing required in individual refining situations. As an 

illustration, distillate desulfurization utilization was less 

than 60 percent in the base case. At the 0.05 percent sulfur 

4-15 
P.98 

level, distillate desulfurization utilization increased by over 

20 percent. In reality, industry utilizations are about 65 

percent (National Petroleum Council, 1985). Thus, it might not be 

possible to reduce diesel fuel sulfur content to 0.05 percent by 

weight without some investment in new desulfurization capacity. 

Another limitation of this analysis is in the area of aromatics 

data. The aromatics content of distillates varies considerably 

between crudes and between refinery intermediate streams, and the 

availability of information on these values is limited. The 

characterization of distillate stream aromatic content in the 

model was based on the limited information available. More 

complete information on the aromatic contents of these streams 

might change the modeling results somewhat, especially for the-.--

low aromatics scenario. The overall conclusions of the model — 

that desulfurization would result in a significant reduction in 

average aromatic content, and that additional reductions could be 

obtained at moderate cost by segregating diesel fuel from #2 

burner oil — are unlikely to be greatly affected, however. 

4-16 
P.99 

5.0: MTO . RRglT.TS AND GDST-EFFBCTIVENESS ANALYSTg 

This chapter defines two scenarios for diesel fuel quality 

regulation, and presents the results of the refining cost model 

for each. It then discusses the resulting effects on the fuel 

economy, durability, and emissions levels of typical diesel 

engines. Estimates of the fuel economy and maintenance savings 

due to the use of the higher-quality fuel are developed for 

typical vehicles in each of five classes: passenger cars, 

light-heavy duty trucks, mediun-heavy duty trucks, line-haul 

trucks, and transit buses. The reductions in particulate and 

sulfur emissions per vehicle due to better fuel quality are also 

estimated for each type of vehicle. These estimates are combined 

with the refining cost results and the estimated maintenance 

savings to calculate the overall costs and cost-effectiveness of 

each scenario. 

S.l EKFINITKH OP THE TVP SCENARIOS 

As the discussion in Chapter Four has indicated, the fuel 

variables having the most important effects on emissions are 

sulfur and aromatics content. Preliminary analyses by both the 

5-1 
p.1 

authors and others (Wall and Hoekman, 1984; CARB, 1984) indicated 

that the cost-effectiveness of reducing the sulfur content was 

likely to be ouch greater than that of reducing the aromatics. 

Furthermore, the major technologies available for reducing 

aromatic content also reduce sulfur (although the converse is not 

true — desulfurization does not necessarily have a significant 

effect on aromatics). For these reasons, we selected two 

scenarios for modeling: one in which only the sulfur content 

would be regulated and a second in which both sulfur and arconatic 

content would be limited. 

Although back-end volatility is often cited as an inportant 

variable in diesel emissions, no scenarios involving changes in 

this variable were modeled. The reasons for this were twofold: 

the evidence linking back-end volatility to emissions is weak; 

and the cost of changing the back-end volatility to reduce 

emissions would be very high. 

For the first scenario, a sulfur limit of 0.05 percent by weight 

was specified, litis value was chosen somewhat arbitrarily as 

roughly the lowest level achievable without severe 

hydrotreating. This is desireable both for cost reasons and to 

ensure that enough polar molecules remain in the fuel to provide 

adequate boundary lubrication in the fuel injection puap. This 

was also the level selected as a sulfur limit for fuel sold in 

the South Coast Air Basin, which provides a convenient 

5-2 
P.2 

harmonization of regulations. It should be clearly noted, 

however, that no optimization studies were carried out in 

choosing this particular sulfur level, and that such studies 

certainly should be done before any such regulation is 

promulgated. The optimal level of control could just as easily 

by 0.03 or 0.07 percent by weight as 0.05. 

The original plan for this study was for the second scenario to 

include the sone 0.05 percent sulfur limit as the first, with an 

additional limit of 22.5 percent on the aromatics content. This 

level was chosen, again somewhat arbitrarily, as being 

approximately the lowest level of aromatics which could be 

achieved by means of changes in blending procedures and 

segregation of diesel fuel frcm burner fuel oil. However, the 

model runs for the first scenario produced the surprising result 

that aromatics would be much lower with desulfurization, even in 

the absence of a specific limit on aromatics. This reduction in 

aromatic content is the result of process and blending changes 

which are necessary to achieve the low sulfur level at minimum 

cost. The aromatic content of the fuels in scenario one turned 

out to be slightly over 20 percent. As a result, the aromatic 

limit for the second scenario was reduced to 17 percent, which 

(according to the model) is a level which can still be achieved 

by blending and segregation alone. 

5-3 
P.3 

5.2 RESULTS FRCM TOE REFINING OT6T MHTFL 

Tables 5.1 through 5.3 compare the refining cost model results 

for the two regulatory scenarios with those for the base case. 

All of the costs and volumes shown in the Tables are annual 

totals for the year 1987. This year was chosen as being about the 

earliest one in which the fuel regulations being modeled could be 

implemented. The costs, and especially the costs-per-gallon 

shown in the tables are considered to be representative of those 

for later years as well. 

As discussed in Chapter Four, PADD V was modeled separately from 

PAEDs I through IV, since pipeline connections between PAED V and 

the remainder of the U.S. are poor. Table 5.1 shows the modeling 

results for PAEDs I through IV, while Table 5.2 shows the results 

for PAED V. Table 5,3 combines the results for the two regions to 

give sums or averages for the entire U.S. 

As has been mentioned, the model results for Scenario One were 

somewhat surprising. As the tables show, the optimal refining 

strategy for producing the given quantity of low-sulfur diesel 

fuel also reduces the fuel's aromatic content from an average of 

28.7 percent to 20.3 percent by volume. This results in an 

increase in API gravity (corresponding to a decrease in density), 

a slight reduction in the volumetric energy content, and an 

increase in the calculated cetane index of the average fuel, 

5-4 
P.4 

Table 5.1: Refining cost model results for PAEDs I through IV. 

Physical Properties 

API Gravity 

Sulfur (wt *) 

Aromatics (vol. %) 

Distillation Tenperatures 

10 percent 

50 percent 

90 percent 

Calculated Cetane Index 

Volumetric energy (M3TU/gal) 

Viscosity (centistokes at 20 C) 

Production and Costs 

Total diesel fuel (NM gal/yr) 

Change in total cost (NM $/yr) 

Change in cost per gallon ($/gal) 

Shadow price of diesel ($/gal) 

Change in shadow price ($/gal) 

34.3 

0.280 

28.4 

418 

520 

605 

47.0 

131.0 

3.1 

15,928 

— 

• — 

0.769 

— 

38.0 

0.048 

20.2 

390 

478 

585 

47.7 

129.0 

2.6 

15,928 

188 

0.012 

0.781 

0.012 

38.0 

0.048 

17.0 

380 

503 

600 

51.2 

129.2 

2.2 

15,928 

236 

0.015 

0.785 

0.016 

5-5 
P.5 

Table 5.2: Refining cost model results for PAED V. 

PhyslcfiT Properties 

API Gravity 

Sulfur (wt %) 

Aromatics (vol. %) 

Distillation Tenperatures 

10 percent 

50 percent 

90 percent 

Calculated Cetane Index 

Volumetric energy (NBTU/gal) 

Viscosity (centistokes at 20 C) 

Production and Costs 

Total diesel fuel (NM gal/yr) 

Change in total cost (NM $/yr) 

Change in cost per gallon ($/gal) 

Shadow price of diesel ($/gal) 

Change in shadow price ($/gal) 

32.5 

0.235 

30.3 

440 

545 

610 

46.7 

131.8 

3.6 

2,537 

— 

— 

0.743 

• — 

34.6 

0.048 

20.7 

440 

545 

610 

50.0 

131.2 

3.4 

2,537 

26 

0.010 

0.764 

0.021 

37.3 

0.048 

17.0 

380 

550 

610 

55.9 

129.6 

3.2 

2,537 

41 

0.016 

0.778 

0.035 

5-6 
P.6 

Table M i Cbrtlned refining ooet model results for the entire U.S. 

Physiol Properties 

API Gravity 

Sulfur (wt %) 

Aromatics (vol. *) 

Distillation Tenperatures 

10 percent 

50 percent 

90 percent 

Calculated Cetane Index 

Volimetric energy (NBTU/gal) 

Viscosity (centistokes at 20 C) 

Production and Costa 

Total diesel fuel (NM gal/yr) 

Change in total cost (NM $/yr) 

Change in cost per gallon ($/gal) 

Shadow price of diesel ($/gal) 

Change in shadow price ($/gal) 

Baseline 

34.0 

0.274 

28.7 

421 

523 

607 

46.0 

131.1 

3.2 

18,465 

__ 

) 

0.765 

Scenario One 

37.5 

0.048 

20.3 

397 

487 

588 

48.2 

129.3 

2.4 

18,465 

214 

0.012 

0.779 

0.014 

Scenario Two 

37.9 

0.048 

17.0 

380 

509 

601 

51.8 

129.3 

2.7 

18,465 

277 

0.015 

0.784 

0.019 

5-7 
P.7 

especially in PAED V. 

The chaise in cetane index is of limited significance — neither 

the cetane index nor the cetane nunber is a linear property, and 

thus the cetane index calculated frcm average properties is not 

the same as the average cetane index. Furthermore, the cetane 

index may differ frcm the cetane nurber by as much as two 

ninnbers. The change in this parameter probably does indicate a 

significant improvement in ignition quality, however, as would be 

expected from the sharp decrease in aromatic content. This 

improvement would be especially marked in PAED V, which includes 

the U.S. Pacific Coast. 

As expected, the data for the second scenario show a further 

reduction in aromatic content, accompanied by a slight decrease 

in density, no change in volunetric energy content, and a 

substantial increase in the calculated cetane index. This would 

produce an extremely high-quality fuel on average. In addition, 

standardization of the aromatic content at 17 percent would 

greatly reduce the variation in density, ignition quality, and 

viscosity between different fuels. As was discussed in Chapter 

Four, this would be a valuable result in itself. 

The cost data shown in Tables 5.1 through 5.3 are of two kinds. 

The first type is the change in total refining costs resulting 

from each scenario, and the change in average cost per gallon of 

5-8 
P.8 

diesel fuel, assuming that the difference in refining costs were 

allocated only to diesel fuel. This is a good measure of the 

social costs (the costs paid by American society considered as a 

whole) of the refining changes in each scenario. 

The second type of cost shown is the change in the "shadow price" 

of diesel fuel calculated by the refinery cost model. If demand 

for diesel fuel were perfectly inelastic and fuel markets were 

perfectly competitive, this would be the change in the market 

wholesale price of diesel fuel as a result of each scenario. 

Since demand for diesel fuel is fairly inelastic and the markets 

are fairly competitive, this is probably a reasonable 

approximation of the price changes that would actually be 

experienced. As the tables show, the change in the shadow price 

is somewhat greater than the change in the average cost, 

especially in PAED V. The difference is due to a decrease in the 

shadow price of distillate burner fuel, which is used as a "sink" 

for the excess aromatics removed from diesel fuel. 

The cost data shown in the tables reflect only the changes in 

refinery operating and raw-materials costs which would result 

from each scenario. Since the model results showed that each 

scenario could be achieved using only the existing refinery 

capacity, no capital or depreciation charges were included in the 

costs. However, this accounting fails to consider the costs of 

minor process and piping changes which would be required to 

5-9 
P.9 

achieve this scenario. The most important of these would be the 

costs associated with segregating the production and distribution 

on diesel fuel and distillate burner fuel. While we were unable 

to quantify these costs within the scope of this study, they are 

considered to be small relative to the changes in operating costs 

presented above. 

The cost estimates for reducing aromatics developed in this study 

are considerably lower than those developed by other workers 

(e.g. CARB, 1984; Chevron, 1984) who considered only the costs of 

applying a new process unit to the existing diesel fuel stream. 

These estimates show the great potential for costs savings 

inherent in the refinery's ability to alter blending and 

processing parameters in order to achieve desired quality 

levels. The extent of this flexibility is borne out by the only 

other similar study of which the authors are aware. This study, 

conducted by Bonner and Moore (1983) and published by the 

American Petroleum Institute, indicated that the average aromatic 

content of diesel fuel in PAED II could be reduced-to about 20 

percent at virtually no cost, and to around 15 percent for less 

than one cent per gallon. This was accomplished by means of 

blending changes, and segregation of distillate burner fuel from 

diesel oil. Some of the results from that study are shown in 

Figure 5.1. 

5-10 
P.10 

l.SO 

1.25 

l.OO0.75 

0.50" 

Average Added 

Cost, S/B3L 

0.25 -• 

10 15 20 25 30 

Ar-omitics Contant, Volume Percent 

Figure 5.1: Refining cost vs. aroeatic content of diesel fuei fron the 

Bonner and Moore study (Bonner and Moore, 1983). 

5-11 
P.11 

5.3 SCENARIO CKF.. rFSUTTTTRIZATICN EFFECTS CK ENGINES AND F^fgJO1 ? 

The results of the refining cost model for Scenario One indicate 

that the reduction in diesel fuel sulfur content to 0.05 percent 

by weight should be accompanied by a reduction in average 

aromatic content as well. Both of these would have beneficial 

effects on emissions. However, as discussed in Chapter Three, 

the refining cost model used is highly aggregated, and the 

results reported are averages over all the refineries in a 

region. Actual refinery processes and crude slates vary, so that 

the reduction in average aromatics due to the sulfur limit in 

this scenario would not be seen in every case. This variation 

would occur due to individual differences in crude mix and 

processing equipment. 

In order to minimize variations in fuel ignition quality, a 

separate limit on aromatic content would be highly desirable even 

in Scenario One. This limit should probably be set at about the 

22 percent level to allow some deviation from the average results 

given in the model, while still minimizing the variation in 

ignition quality. The incremental cost of such a limit cannot be 

cooputed from the model in its present form, since it would 

involve no change in the mean aromatic content, just a reduction 

in its variation. The cost would probably be quite low, however, 

since the capacity to achieve it exists with the present capital 

stock. 

5-12 
P.12 

Reducing the sulfur content of diesel fuel would directly reduce 

diesel emissions of SO and particulate sulfates. Frcm the data 

2 

in Table 5.3, these reductions would amount to more than 80 

percent of the total, or about 285,000 tons per year of SO and 

2 

about 7,000 tons per year of particulate sulfates nationwide. 

Since the sulfur content of diesel fuel is generally expected to 

increase in the future, the actual reductions from a low-sulfur 

standard might be even greater. The reduction in SO emissions 

2 

would result in a corresponding decrease in the formation of 

secondary sulfate particles, acid deposition, and materials 

damage due to sulfur. 

The reduced SO concentration in the exhaust gas would also 

2 

permit the use of more active catalysts in catalytic 

trap-oxidizers, making the design of catalytic traps much easier, 

and indirectly reducing HC, CO, odor, and particulate emissions 

from trap-equipped vehicles. Desulfurization would thus be very 

helpful in meeting EPA's 1991 particulate standard of 0.25 

g/BHP-hr for heavy-duty truck engines; it would probably be 

essential for meeting the 0.1 g/BHP-hr standard for transit bus 

engines. 

Reducing the sulfur content of diesel fuel would result in 

reduced corrosive wear of cylinders, rings, and bearings. This 

would help to increase the time between overhauls in heavy-duty 

5-13 
P.13 

engines, and would extend total engine life in both light and 

heavy-duty vehicles. Although there is universal agreement on 

the qualitative effects of this change, quantitative data 

supporting it are scarce. The best data available are those of 

Tennyson and Parker (1970), which were discussed in Chapter Four. 

Those results (which are probably conservative) indicate a 30 to 

40 percent reduction in wear rates with the use of fuel 

containing 0.05 percent rather than 0.27 percent sulfur. For the 

cost-effectiveness calculations in this study we have assumed a 

30 percent extension in mileage between overhauls and in total 

engine life. We consider this to be a reasonably conservative 

estimate. 

In addition to reduced corrosive wear, a lower sulfur content 

would help to reduce deposit formation on the pistons and other ~ 

critical parts. This, combined with the reduced acid loading in 

the engine oil might also make it possible to extend oil change 

intervals and/or to reduce the alkaline ash content of the oil. 

The former would be desirable in order to reduce costs and the 

environmental problems of used-oil disposal, while the latter 

would help to extend trap-oxidizer life. Reduced deposit 

formation would also help to improve oil control, reduce oil 

consuiption, and increase engine life. 

The reduction in aromatics content which would result frcm 

desulfurization would also have a beneficial effect on 

5-14 
P.M 

emissions. Extrapolating from the data developed by Barry et 

alia_(1985), we estimate that the reduction in average aromatic 

content from 28.7 to 20.3 percent should result in a 22 percent 

decrease in the carbonaceous (non-sulfate) fraction of the 

particulate material in heavy-duty engines. The data of Bykowski 

and co-workers (1983) indicate an effect of similar magnitude for 

light-duty engines, although this is highly engine-dependent. 

The reduced soot production in the engine would reduce the soot 

content of the blowby, reducing soot fouling and contsmination of 

the oil. This would also help to reduce oil change frequency. 

The reduced aromatics and inproved cetane nunber s with this 

scenario would improve cold-starting and idling performance and 

reduce engine noise. The reduction in the use of catalytically 

cracked blending stocks would also be expected to have a 

beneficial effect on deposit-forming tendencies in the fuel 

injectors, reducing the maintenance requirements for these 

parts. On the negative side, the reduction in average aromatic 

content might result in some inpairment of cold-flow properties 

due to the increased paraffin content of the fuel. This would be 

offset to some extent by the reduction in 90-percent point in 

this scenario. 

The lower density of the fuel in this scenario, resulting from 

the lower density of paraffinic than aromatic hydrocarbons, would 

reduce the volunetric energy content somewhat, resulting in 

5-15 
P.15 

slight increase in volumetric fuel consuiption if all other 

factors were to remain equal. From the data in Table 5.3, this 

would amount to a loss of about 1.4 percent in fuel economy. On 

the other hand, the inproved and more consistent ignition quality 

of the fuel would make it possible to improve fuel efficiency 

somewhat, at least in new or newly rebuilt engines. This could 

be done by small timing inprovements to optimize NOx control for 

the higher-cetane fuel, and by slightly reducing the compression 

ratio. In addition, the inproved cold-starting capability of the 

higher-cetane fuel would reduce fuel wastage in cold start and 

warmup operations. Thus the overall effects on fuel economy 

would probably be positive. 

5.4 SOKARIO TWO: DEAKMATIZATICK EFFECTS CK BONE S AND EMISSION 

Scenario Two includes all of the actions in Scenario One, plus a 

further reduction in aromatics content. It is therefore most 

appropriate to consider the incremental costs and benefits of 

Scenario Two as compared to Scenario One, rather than coopering 

it to the baseline. All of the beneficial effects of 

desulfurization noted for Scenario One would also apply to this 

scenario, as would the effects (good and bad) of decreased 

aromatic content. These latter effects are, in general, greater 

in this scenario than in Scenario One, however. 

5-16 
P.16 

The additional reduction in fuel aromatic content in Scenario Two 

would result in a further reduction in particulate compared to 

Scenario One. From the data in Barry et alia (1985), a reduction 

in the carbonaceous fraction of the particulate of about 31 

percent (compared to the baseline) would be expected. This 

represents an additional nine percentage points beyond the 

reduction estimated for Scenario One. There would also be seme 

further reduction in hydrocarbon emissions. 

The incremental maintenance benefits over Scenario One would be 

minor. A further reduction in soot-fouling of the oil and in 

deposit formation in the injectors would be expected, but the 

effect of these would not be great. Cold start performance would 

be further improved with this scenario, resulting in still 

greater reductions in hydrocarbon emissions. On the other hand, 

the decreased aromatics and higher 90 percent point with this 

scenario would further impair the cold-flow properties of the 

fuel, and this might prove troublesome in winter operation. The 

volumetric energy content for this scenario is little changed 

from Scenario One, and thus the effects on fuel economy would be 

about the same. A small further increase in fuel economy in new 

engines through tighter calibration for NOx and a lower 

compression ratio might be possible, however. 

5.5 qQST-EFFECTIVFUESS OF FUEL QUALITY RFffiTATTfNS 

5-17 
P.17 

This section develops some approximate comparisons of the fuel, 

maintenance, depreciation, and other costs of operating each of 

five typical vehicles for the baseline case and for each of the 

two scenarios discussed above. These comparisons are shown in 

Tables 5.4 through 5.8. It should be noted that the cost and 

emissions changes and the cost-effectiveness values in these 

tables are shown as the incremental changes from the baseline to 

Scenario One, and from Scenario One to Scenario Two. The specific 

assumptions going into these tables are discussed below. 

The values shown in Tables 5.4 through 5.8 are considered to be 

reasonable estimates, and are generally somewhat conservative in 

that they have tended to err toward understating benefits and 

overstating costs where these were doubtful. It should be borne 

in mind, however, that many of the estimated effects shown are 

based on incompleted data, and should thus be interpreted 

cautiously. The tables also fail to account for some 

difficult-to-quantify benefits, such as reductions in injector 

deposits and improvements in cold starting performance. 

Despite these weaknesses, the results shown in Tables 5.4 through 

5.8 make a strong case for action to reduce diesel fuel sulfur 

and aromatic content. For the first scenario, these tables 

indicate that substantial net benefits would accrue from 

desulfurization and dearomatization of diesel fuel, even 

5-18 
Table 5.ft; Fuel coata, maintenance benefits and cost-effectiveness of fuel 

regulations for a typical light-duty car or truck. 

Fuel and Maintenance Coats 

Lifetime mileage 

Miles/year 

Discount rate 

Equivalent cost factor 

Fuel economy (mpg) 

Fuel cost (t/eal) 

Total annual cost 

Oil change frequency (mi) 

Cost of oil change (§) 

Annual ccst 

Engine cost (new) 

Equivalent annual cost 

Total annual cost 

Change from previous 

flflawltwm and fn.^t-gffftfttlv«ne»a 

Particulates (&/aile) 

Carbonaceous 

Direct Sulfate 

Total Direct Part. 

SC? emissions (g/mile) 

Icairect Part, (g/mile) 

Baseline 

100,000 

15,000 

0.100 

0.213 

28.000 

1.130 

605.36 

5,000 

20.00 

60,00 

4,000.00 

850.56 

1,515.92 

130,000 

15,000 

0.1C0 

0.178 

28.000 

1.145 

613.39 

6,500 

20.00 

46.15 

4,000.00 

711.47 

1,371.02 

(144.90) 

SceoarifiJTaa 

130,000 

15,000 

0.1C0 

0.178 

28.000 

1.148 

615.00 

6,500 

20.00 

46.15 

4,000.00 

711.47 

1,372.63 

1.61 

0.31 

0.04 

C.35 

0.60 

Total Part. ($/mile) 

Total annual Part, (lb) 

Reduction from prev. (lb/yr) 

Ccst-Effectiveneas Ct/lb) 

1.08 

35.52 

0.2U 

0.C1 

0.25 

0.11 

0.13 

0.38 

12.42 

23.10 

t6.27) 

0.21 

0.01 

0.22 

0.11 

0.13 

0.35 

11.50 

0.92 

1.74 

5-19 
P.19 

. . v.,.-, ~,«t» M-UWiianc. b.Mflta and co.t-.fr.etly.MM of fu.l 

« "

 W, -SSlSJ2 : S » W- l U*W— » duty truck. 

^,^1 and rfrjptenanc.e Coata 

Lifetime mileage 

Miles/year 

Discount rate 

Equivalent cost factor 

Relative Fuel Consumption 

Fuel economy (npg) 

Fuel cost U/gal) 

Total annual cost 

Oil change frequency (mi) 

Cost of oil change ($) 

Annual cost 

Engine cost (new) 

Equivalent annual cost 

USSUBS. ^fnarlo One SflfiflMifl-Iia 

120,000 

20,000 

0.100 

0.230 

1.000 

14.650 

1.130 

1,542.66 

5,000 

25.00 

1C0.00 

6,000.00 

1,377.64 

156,000 

20,000 

0.1C0 

0.191 

1.000 

14.650 

1.145 

1,563.1* 

6,500 

25.CO 

76.92 

6,000.00 

1,143.91 

156,000 

20,CC0 

0.1C0 

0.191 

1.000 

14.650 

1.148 

1,567.24 

6,500 

25.00 

76.92 

6,000.00 

1,143.91 

Total annual cost 

Change from previous 

3,020.31 2,783.98 

(236.33) 

2,783.07 

..... a. 10 

Particulates (g/SKP-hr) 

Carbonaceous 

Direct Sulfate 

Total Direct Fart. 

EEP-hr per Rile 

Direct part. (7/nile) 

SO, emissions (s/raile) 

Irlirsct Part, (g/aile) 

C.56 

0.04 

C.60 

0.89 

C.53 

1.15 

1.39 

0.^4 

0.C1 

0.14 

0.59 

C.39 

0.20 

0.24 

0.39 

0.C1 

0.39 

0.89 

C.35 

0.20 

0.24 

Total Part, (c/xile) 

Total annual Part, (lb) 

Reduction frcm prev. (lb/yr) 

Cost-Effectiver.ess ($/lt; 

1.92 

84.57 

0.64 

28.Q9 

56.48 

(4.18) 

0.59 

26.12 

1.98 

2.07 
Tabl* 5-*6: Fuel costs, maintenance benefits and cost-effectiveness of fuel 

regulations for a typical aediua-heary truck. 

Lifetime mileage 

Miles/year 

Discount rate 

Equivalent cost factor 

Relative Fuel Consumption 

Fuel economy (mpg) 

Fuel cost ($/gal) 

Total annual cost 

Oil change frequency (mi) 

Cost of oil change ($) 

Annual cost 

Engine cost (new) 

Equivalent annual cost 

Mileage to overhaul 

Cost of Overhaul 

Equivalent annual coat 

Total annual cost . 

Change from previous 

400,000 

40,000 

0.100 

0.163 

1.000 

7.780 

1.130 

5,809.77 

11,000 

35.00 

127.27 

9,000.00 

1,464.71 

221,000 

3,000.00 

288.36 

7,690.11 

Scenario One 

520,000 

40,000 

0.100 

0.141 

1.000 

7.780 • 

1.145 

5,886.89 

15,000 

35.00 

93.33 

9,000.00 

1,267.01 

287,300 

3,000.00 

212.99 

7,460.22 

(229.89) 

trfflrffi"iO TW O 

520,000 

40,000 

0.100 

0.141 

1.000 

7.780 

1.148 

5,902.31 

15,000 

35.00 

93.33 

9,000.00 

1,267.01 

287,300 

3,000.00 

212.99 

7,475.64 

15.42 

^ " 1" " - »"* ftt«t-KffMtlWlJM 

Particulates (g/BHP-hr) 

Carbonaceous 

Direot Sulfate 

Total Direct Part. 

BHP-hr per mile 

Direct part, (g/mile) 

S02 emissions (g/mile) 

Indirect Part, (g/mile) 

0.75 

0.05 

0.80 

2.07 

1.66 

2.17 

2.61 

4.27 

375.81 

0.58 

0.01 

0.59 

2.07 

1.23 

0.38 

0.46 

1.69 

148.56 

227.24 

0.52 

0.01 

0.53 

2.07 

1.09 

0.38 

0.46 

1.55 

136.25 

12.31 

Total Part, (g/mile) 

Total annual Part, (lb) 

Reduction froa prev. (lb/yr) 

Cost-Effectiveness ($/lb) (1.01) 1.25 

G-Ol 
Tabla 5.7: Fuel costs, aaintenance benefits and cost-effectiveness of fuel 

regulations for a typical line-haul truck. 

P.21 

Pn«l and Malnfr.-anan-Rfl CQ?t? 

Lifetime mileage 

Miles/year 

Discount rate 

Equivalent cost factor 

Relative Fuel Consumption 

Fuel economy (mpg) 

Fuel cost ($/gal) 

Total annual cost 

Oil change frequency (mi) 

Cost of oil change ($) 

Annual cost 

Engine cost (nev) 

Equivalent annual cost 

Mileage to first overhaul 

Cost of Overhaul 

Equivalent annual cost 

Mileage to second overhaul 

Cost of Overhaul 

Equivalent annual cost 

Total annual cost 

Change from previous 

^ifltllnt 

800,000 

100,000 

0.100 

0.187 

1.000 

5.670 

1.130 

19.929.U5 

13,000 

50.00 . 

384.62 

20,000.00 

3,748.88 

300,000 

5,000.00 

704.15 

550,000 

10,000.00 

1,109.72 

25,876.81 

ftrlftfllannj* and COflt-Eff-SfifciYeneaS 

Particulates (g/BHP-hr) 

Carbonaceous 

Direot Sulfate 

Total Direct Part. 

BHP-hr per mile 

Direct part, (g/mile) 

SO. emissions (g/mile) 

Indirect Part, (g/mile) 

Total Part, (g/mile) 

Total annual Part, (lb) 

Reduction froo orev. (lb/yr) 

0.75 

0.05 

0.80 

3.12 

2.50 

2.98 

3.58 

6.08 

1338.44 

1,040,000 

100,000 

0.100 

0.159 

1.000 

5.670 

1.145 

20,194.00 

17,000 

50.00 

294.12 

20,000.00 

3,180.26 

390,000 

5,000.00 

548.24 

715,000 

10,000.00 

804.41 

•25,021.03 

(855.78) 

0.58 

0.01 

.0.59 

3.12 

1.85 

0.52 

0.63 

2.48 

546.20 

792.23 

S<v««qrio Two 

1,040,000 

100,000 

0.100 

0.159 

1.000 

5.670 

1.148 

20,246.91 

17,000 

50.00 

294.12 

20,000.00 

3,180.26 

390,000 

5,000.00 

548.24 

715,"000 

10,000.00 

804.41 

25,073.94 

52.91 

0.52 

0.01 

0.53 

3.12 

1.64 

0.52 

0.63 

2.27 

499.82 

46.3$ 

Cost Effectivenesses/lb) (1.08) I.K 
Table 5.8: Fuel costs, oaintenance benefits and cost-effectiveness of fuel 

regulations for a typical transit bus. 

FUfll ffT"1 tfcHnfciiQa.Q'-Qf Coata 

Lifetime mileage 

Miles/year 

Discount rate 

Equivalent cost factor 

Relative Fuel Consumption 

Fuel economy (mpg) 

Fuel cost ($/gal) 

Total annual cost 

Oil change frequency (mi) 

Cost of oil change ( H 

Annual cost 

Engine cost (new) 

Equivalent annual cost 

Mileage to first overhaul 

Cost of Overhaul 

Equivalent annual cost 

Mileage to second overhaul 

Cost of Overhaul 

Equivalent annual cost 

Total annual cost 

Change from previous 

RBiaair-in* and Coat-Kffaatlveneai 

Particulates (g/BHP-hr) 

Carbonaceous 

Direct Sulfate 

Total Direct Part. 

500,000 

40,000 

0.100 

0.144 

1.000 

4.000 

0.920 

9,200.00 

8,000 

50.00 

250.00 

16,000.00 

2,298.20 

180,000 

8,000.00 

748.33 

350,000 

8,000.00 

499.08 

12,995.61 

I 

0.75 

0.05 

0.80 

Scenario One 

650,000 

40,000 

0.100 

0.127 

1.000 

4.000 

0.935 ' 

9,350.00 

10,000 

50.00 

200.00 

16,000.00 

2,031.76 

234,000 

8,000.00 

581.69 

455,000 

8,000.00 

343.56 

12,507.01 

(488.59) 

0.58 

0.01 

0.59 

krfftTiario T w 

650,000 

40,000 

0.100 

0.127 

1.000 

4.000 

0.938 

9,380.00 

10,000 

50.00 

200.00 

16,000.00 

2,031.76 

234,000 

8,000.00 

581.69 

455,000 

8,000.00 

343.56 

12,537.01 

30.00 

0.52 

0.01 

0.53 

BHP-hr per mile 

Direct part, (g/mile) 

4.40 

3.52 

4.40 

2.61 

4.40 

2.32 

SO- emissions (g/mile) 

Indirect Part, (g/mile) 

Total Part, (g/mile) 

Total annual Part, (lb) 

Reduction from prev. (lb/yr) 

4.23 

5.08 

8.60 

757.30 

0.74 

0.89 

3.50 

308.52 

448.78 

0.74 

0.89 

3.20 

282.35 

26.17 

Cost Effectiveness (1.09) 1.15 
exeindipy ^py mi^inn s benefits. In addition to the benefit to 

society at large from reduced emissions, inproved fuel quality 

would directly benefit vehicle owners through reduced maintenance 

costs and increased engine lifetime. These benefits outweigh the 

increase in fuel cost due to improved quality for every class of 

vehicles considered. 

Scenario Two calls for additional dearomatization beyond the 

level in Scenario One. This would result in a slight further 

increase in fuel costs, and a further reduction in carbonaceous 

particulate emissions. The incremental cost-effectiveness of 

this further step would be about $5.50 to $10.00 per pound of 

particulate removed, depending on the which vehicle class is 

being considered. For comparison, EPA (1984) has estimated the -

cost-effectiveness of the new heavy-duty engine particulate 

standards for 1988 and 1991 at $0.21 and $1.75 to $2.60 per 

pound, respectively. Many observers (including the ERC authors 

of this report) consider these last figures to be understated by 

a factor of two or three, which would bring the 

cost-effectiveness of the trap-oxidizer standard into the same 

range as the cost-effectiveness of additional aromatic controls. 

It should be recognized that there is considerable uncertainty in 

these values, however, and additional detailed study is strongly 

recomnended. 

The data in Tables 5.4 through 5.8 represent typical vehicles of 

5-24 
P.24 

roughly 1982 vintage in each class. This is reflected in the 

estimates of miles per gallon and of EHP-hr per mile shown for 

heavy-duty trucks, which were taken from Energy and Environmental 

Analysis (1983). The factors for buses and light-duty vehicles 

are estimates by the authors. Similarly, the emissions factors 

(g/mi or g/EHP-hr) shown in the tables are typical for several 

year old engines which are now in use. For the heavy-duty 

vehicles, these emission factors are based on test data showing 

that typical in-use emissions from properly maintained engines 

are about 0.8 g/EHP-hr (EMA, 1985). 

The major assmptions made in developing Tables 5.4 through 5.8 

concern the effects on fuel costs; the effects of reducing fuel 

sulfur on engine life, time between overhauls, and oil life; -and~-

the effects of reducing aromatic content on particulate emissions 

and fuel economy. The fuel cost changes shown were developed by 

taking the average cost increases shown in Table 5.3 and adding 

0.3 cents per gallon to each to allow for overoptimization and 

the capital costs of segregating diesel from burner fuel. These 

estimates thus represent the increased social cost of the 

refining changes. As Table 5.3 shows, the change in social cost 

is not greatly different from the estimated change in the market 

price of the fuel (represented by the change in its shadow 

price). Use of the market price would change the magnitudes of 

the costs shown, but would not affect the conclusions. 

5-25 
P.25 

In developing the tables, the change from 0.274 percent to 0.048 

percent sulfur in the fuel was assumed to extend engine life, oil 

life, and time between overhauls by 30 percent. The baseline 

data on time between overhauls for heavy-duty trucks were 

obtained frcm a study ccomissioned by the EMA (Survey Dara 

Research, 1981), while the overall engine lifetimes shown were 

estimated by the authors. Representative data on the costs of 

overhauling different classes of engines were obtained from an 

experienced diesel mechanic (D. Decker, Colo. Dept of Health, 

personal coamunication). Data on the costs of the engines 

themselves were taken from Galef (1984). The costs of oil changes 

for each class of engine were estimated by the authors. 

The reduction in the fuel aromatic content from 28.7 to 20.3 

percent in Scenario One was assuned to result in a 22 percent 

reduction in the carbonaceous (soot plus organic) fraction of the 

particulate matter. The reduction to 17 percent aromatics in 

Scenario Two was assuned to give a further 9 percent reduction in 

the carbonaceous fraction, for a total reduction of 31 percent 

from the baseline. These changes were assuned to have no effect 

on fuel economy — it was assuned that the slight reduction in 

volumetric energy content due to the lower aromatic content would 

be offset by improved efficiency due to better ignition quality. 

5-26 
P.26 

6.0: mruusios AND rami/MFNrwrKis 

This study has examined the feasibility, costs, and maintenance 

benefits of two possible diesel fuel quality regulations, and has 

examined their cost-effectiveness for emissions control. The 

following conclusions can be stated. 

(1) The most important emissions-related properties 

of diesel fuel are the sulfur content and the 

fraction of aromatic hydrocarbons. Reducing fuel 

sulfur would reduce SO emissions and the sulfate 

fraction of diesel particulates, and would 

indirectly reduce ambient levels of sulfate 

particles. Reducing fuel aromatic content would 

reduce the carbonaceous fraction of diesel 

particulate emissions. Contrary to cannon 

belief, changes in the distillation tenperatures 

(such as the 90 percent point and end point) have 

little potential for emissions control. 

(2) It would be feasible to reduce the sulfur content 

of automotive diesel fuel from the present 

average of about 0.274 percent to 0.048 percent 

by weight. This could be done without reducing 

the availability of diesel fuel, and could 

probably be done using only the present capital 

stock. This would require segregating production 

of diesel fuel from that of distillate burner 

fuels, as well as high rates of utilization of 

existing desulfurization capacity. The increase 

in average refining cost due to desulfurization 

would be about 1.2 cents per gallon. 

(3) Desulfurization of diesel fuel to 0.048 weight 

percent as in (1) would also produce a decrease 

in the average aromatic content of diesel fuel, 

6-1 
P.27 

from the present 28.7 percent to 20.3 percent by 

volune. Since refinery processes differ, this 

reduction would not be seen in every case. In 

order to minimize variations in ignition quality, 

a separate limit on aromatics content would be 

desirable. The cost of such a limit would be 

small if it were set somewhat above the average 

aromatic content. 

(3) Reducing the sulfur content of diesel fuels would 

reduce corrosive wear and oil fouling and would 

extend engine life. These benefits are difficult 

to quantify due to a lack of applicable 

quantitative data. However, a conservative 

estimate based on the limited data available 

indicates that the savings due to reducing sulfur 

to 0.048 percent would be about four times the 

increase in refining costs. Substantial 

reductions in SO emissions and ambient sulfate 

particles would Also occur. 

(4) The lower aromatic content resulting from 

desulfurization would improve cetane nurbers and 

ignition quality. This would aid cold starting 

and reduce noise, and might make possible changes 

in engine design and calibration that would 

improve fuel economy. The reduction in aromatics 

would also result in roughly a 22 percent 

decrease in carbonaceous particulate emissions 

from heavy-duty diesel engines. The reduction in 

light-duty particulate emissions is uncertain, 

but would probably be similar. 

(5) It would be feasible to reduce the aromatic 

content of diesel fuel below the level attained 

with desulfurization. A reduction to 17 percent 

aromatics could be achieved using the present 

capital stock, and would increase refining costs 

by about 0.4 cents per gallon beyond the level 

that would be experienced with desulfurization. 

This would result in minor further improvements 

in cold starting and other performance 

characteristics, but.might cause cold flow 

problems at low tenperatures. Carbonaceous 

particulate emissions would also be reduced by 

about a further nine percent of the baseline. 

The incremental cost of particulate control by 

this means would be about $5.50 to $10.00 per 

pound of particulate matter eliminated. This is 

6-2 
P.28 

three to five times as great as EPA's estimate of 

the cost per pound of diesel particulate matter 

eliminated by trap-oxidizers on heavy-duty 

vehicles. 

Bficam£odAliojQ& 

It appears that lower limits on diesel fuel sulfur and aromatic 

content could produce significant reductions in emissions while 

saving money for U.S. society. Furthermore, these limits could 

be attained quickly, using the existing capital stock. It is 

recoomended that EPA consider establishing such limits through 

regulation or other appropriate means. The numerical limits on 

sulfur and aromatics content considered in this report were 

selected judgementally, and may not represent global optima. 

Additional detailed studies in this area would be desirable in 

order to define the socially optimal limits for these 

quantities. 

The conclusions of this report rely heavily on estimates of the 

reduction in wear rates due to use of low-sulfur fuel and of the 

reduction in particulate emissions due to lower aromatic 

content. Neither estimate is wholly satisfactory, due to the 

limited data available. Further research on the effects of low 

vs. moderate sulfur fuels on engine life would be highly 

desirable, as would additional carefully-designed studies of the 

relationships between aromatic content and particulate emissions 

in a variety of heavy-duty engines. Finally, existing data on 

6-3 
P.29 

the relationships between light-duty particulate emissions and 

aromatics should be reanalyzed to account for the effects of 

sulfur. 

6-4 
BIBLIOGRAPHY 

Barry, E.G., L.J. McCabe, D.H. Gerke, and J.M. Perez (1985) 

"Heavy-Duty Diesel Engine/Fuels Combustion Performance and 

Emissions: A Cooperative Research Program", SAE Paper #852078 

in Diesel Fuel Q^llty and Trends. SP-639, Society of 

Automotive Engineers, Warrendale, PA. 

Bergin, S.P. (1983) "The Influence of Fuel Properties and Engine 

Load Upon the Carbon and Hydrocarbon Fractions of Particulate 

Emissions from a Light Duty Diesel Engine", SAE Paper #831736 

in Combustion of Heterogeneous Mixtures. SP-557, Society of 

Automotive Engineers, Warrendale, PA. 

Blanc,. L.A. (1947) "Effect of Diesel Fuel on Deposits and Wear", 

SAE QmpteH y Transactions, Vol. 2, No. 2, April, 1948, pp 

306-315. 

Bonner and Moore Management Science (1983) Refining and 

Downstream Impacts of Modifying Diesel Fuel Qialities (3 

volumes), Publication No. 4361, American Petroleum Institute, 

Washington, D.C. 

Bykowski, B.B., CT . Hare, R.L. Mason, and T.M. Baines (1983) 

"Comparison of Petroleum and Alternate-Source Diesel Fuel 

Effects on Light-Duty Diesel Emissions", SAE Paper #831712, 

Society of Automotive Engineers, Warrendale, PA. 

Chevron Research Company (1984) "Fuel Composition Effects on 

Diesel Particulate Emissions", slides from a presentation to 

the U.S. Environmental Protection Agency, June 18, 1984. 

Cloud, G.H., and A.J. Blackwood (1943) "The Influence of Diesel 

Fuel on Engine Deposits", SAE Journal (Transactions), Vol 51, 

No. 11, November, 1943. 

Collins, J.M. and G.H. Unzelman (1982) "Diesel Trends Emphasize 

Cetane Economics, Quality and Prediction", presented at the 

47th Mid-Year Refining Meeting, API Order No. 820-00002, 

American Petroleum Institute, New York, NY. 

Cummins Engine Coapany (1984) statement to California Air 

Resources Board October 25, 1984. 

Daimler-Benz AG (1984) "Control of Diesel Engine Emissions by 

Diesel Fuel Modifications", comments of Daimler-Benz AG at the 

CARB Consultation Meeting, Sacramento, CA, May, 1984. 

Dyson, A., L.J. Richards, and K.R. Williams (1957) "Diesel Engine 

Lubricants: Their Selection and Utilization with Particular 

Reference to Oil Alkalinity", Proceedings of the Institution of 

BIB-1 
P.31 

Mechanical Engineers. Vol. 171, No. 23. 

Dorn, P. and A.M. Mourao (1984) "The Properties and Performance 

of Modern Automotive Fuels", SAE Paper #841210, Society of 

Automotive Engineers, Warrendale, PA. 

Energy and Environmental Analysis, Inc. (1983) "Historical And 

Projected Emissions Conversion Factor And Fuel Economy For 

Heavy-Duty Trucks 1962-2002", Motor Vehicle Manufacturers 

Association, Detroit, Michigan. 

Engine Manufacturer's Association (1985) "Heavy Duty Diesel 

Engine In-Use Emission Testing", presentation to the California 

Air Resources Board Staff, September 11, 1985, El Monte, CA. 

Fortnagel, M., H.O. Hardenburg, and M. Gairing (1982) 

"Requirements of Diesel Fuel Quality: Effects of Poor Quality 

Fuels", American Petroleun Institute, New York. 

Furs toss, R.J. (1948) "Field Experience With High Sulfur Diesel 

Fuels", SAE Quarterly Transactions, Vol. 3, No. 4, October, 

1949. 

Galef, B. (1984) T^e Economic Impacts of MPx and Particulate 

Mutter Emissions Regulations on the Heavy-Pity Diesel Engine 

Industry, report to the U.S. EPA, Sobotka and Ccnpany, 

Washington, DC. 

Gergel, W.C. (1980) "Interrelation of Diesel Engine Lubricant 

Quality and Sulfur Content of Diesel Fuel", Paper #FL-80-83, 

National Petroleum Refiners Association, Washington, DC. 

Glavincevski, B., O.L. Gulder, and L. Gardner (1984) "Cetane 

Nunber Estimation of Diesel Fuels from Carbon Type Structural 

Composition", SAE Paper #841341 in Alternative Fuels for 

Compression and s.l. Engines. SP-587, Society of Automotive 

Engineers, Warrendale, PA. 

Hardenburg, H.O. (1985) statement before the California Air 

Resources Board syoposiun on diesel vehicle emission control, 

June 27, 1985. 

Hare, CT . (1985) Study of the Effects of Fuel ConposiHon. and 

Tnfaattnn and (Valuation Systan Type and Adjustmentr nn Exhaust 

WnJaatftna from Light-Qity Diesels, final report to the 

Coordinating Research Council for Project CAPE-32-80, Southwest 

Research Institute, San Antonio, TX. 

Hilden, D.L., S.P. Bergin, H.A. Bur ley, R.D. Thar by, and I.P. 

Fisher (1982) "The effect of Hydrotreatment of Diesel Fuel 

Derived from Canadian Tar Sands on Particulate Exhaust 

Emissions", SAE Paper #821243, Society of Automotive Engineers, 

BIB-2 
Warrendale, PA. 

Kagami, M., Y. Akasaka, K. Date, and T. Maeda (1984) "The 

Influence of Fuel Properties on the Performance of Japanese 

Automotive Diesels", SAE Paper #841082, Society of Automotive 

Engineers, Warrendale, PA. 

Kamel, M.M. (1984) "Effects of Fuel Ignition Improvers in Diesel 

Engine Performance", SAE Paper #840109, Society of Automotive 

Engineers, Warrendale, PA. 

Lax, D. (1981) "Analysis of Fuel Economy and Vehicle Use Data for 

the 1977 Truck Inventory and Use Survey", SAE Paper #810388, 

Society of Automotive Engineers, Warrendale, PA. 

Lilly, L.R.C. (1984) Diesel Engine Reference Rnokr Butterworths, 

London, U.K. 

McGeehan, J.A., B.J. Fontana, and J.D. Kremer (1983) "The Effects 

of Piston Tenperature and Fuel Sulfur on Diesel Engine Piston 

Deposits", SAE Paper #831721, Society of Automotive Engineers, 

V/arrendale, PA. 

McMillan, M.L. (ed.) (1983) Matching Diesel Fuel Quality to 

Diesel Engine Requirements. SP-577, Society Of Automotive 

Engineers, Warrendale, PA. 

Moulton, D.S. and N.R. Sefer (1984) Diesel Fuel Quality and 

Effects of Fuel Additives. Synthesis of Transit Practice #3, 

Transportation Research Board, National Research Council, 

Washington, D.C. 

Olree, R.M. and D.L. Lenane (1984) "Diesel Combustion: Cetane 

Nunber Effects", SAE Paper #840108, Society of Automotive 

Engineers, Warrendale, PA. 

Peugeot S.A. (1984a) "Diesel Fuel Quality and Inpact on Emissions 

and Engine Operation", photocopy, Peugot S.A. Etudes et 

Recherches, La Garenne-Colcntoes, France. 

(1984b) statement to California Air Resources Board 

at the consultation meeting to discuss the control of diesel 

engine emissions by diesel fuel modifications, May 8, 1984. 

Phatak, R. and T. Nakaoura (1983) "Cold Startability of 

Open-Chamber Direct-Injection Diesel Engines—Part I: 

Measurement Technique and Effects of -Compression Ratio", SAE 

Paper #831335 in A Worldwide Yiew of Dleael Ctflfeugtlon. 

Fmission«f and Analyaiar P-130, Society of Automotive 

Engineers, Warrendale, PA. 

Plee, S.L. and T. Ahmad (1983) "Relative Roles of Premixed and 

BIB-3 
P.33 

Diffusion Burning in Diesel Coirbustion", SAE Paper #831733 in 

Caiteuation nf Heterogeneous Mixtures. SP-557, Society of 

Automotive Engineers, Warrendale, PA. 

Pless, L.G. (1984) letter to H.B. Weaver (Motor Vehicle 

Manufacturer's Association), March 7, 1984. 

Regneault, M., J. Perez, and G. Cahill (1983) "Combustion Quality 

Improvements of Diesel Fuel by Additivation", presented at the 

AGELFI Conference, Brussels, Belgium, October 1983. 

SAE (1984) "Diesel Fuels", SAE Information Report SAE-J313 JUN84 

in SAF. Hsndhnnif. Volune 3, Society of Automotive Engineers, 

Warrendale, PA. 

Sachdev, R., V.W. Wong, and S.M. Shahed (1984) "Analysis of 

Regeneration Data for a Cellular Ceramic Particulate Trap", SAE 

Paper #840076 in Diesel Particulate Traps. P-140, Society of 

Automotive Engineers, Warrendale, PA. 

Schmidt, G.K. and E.J. Forster (1984) "Modern Refining for 

Today's Fuels and Lubricants", SAE Paper #841206, Society of 

Automotive Engineers, Warrendale, PA. 

Seizinger, D.E., W.F. Marshall, and A.L. Brooks (1985) "Fuel 

Influences on Diesel Particulate", SAE Paper #850546, Society 

of Automotive Engineers, Warrendale, PA. 

Shelton, E.M. and CL . Dickson (1984a) "Diesel Fuel Oils, 1984", 

NIPER-137 PPS National Institute for Petroleum and Energy 

Research, Bartlesville, CK. 

Shelton, E.M. and CL . Dickson (1984a) "Heating Oils, 1984", 

NIPER-136 PPS National Institute for Petroleum and Energy 

Research, Bartlesville, CK. 

Sprogus, W.A. "Possibilities to Reduce Influence of Compression 

Ratio on Total Hydrocarbon Emissions from a D.I. Diesel 

Engine", SAE Paper #831293 in A Worldwide View of Diesel 

Onrtmitlon. Rnlaaiona. and Analysis, P-130, Society of 

Automotive Engineers, Warrendale, PA. 

Steere, D.E. (1984) "Development of the Canadian General 

Standards Board (CGSB) Cetane Index", SAE Paper #841344, 

Society of Automotive Engineers, Warrendale, PA. 

Strange, H.O. (1982) "Diesel Fuel Quality and Trends", Paper 

#FL-82-83, National Petroleun Refiner's Association, 

Washington, D.C. 

Survey Data Research (1981) A Study to Determine Diesel Rehuild 

Criteria Among Owners of Diesel Powered Vehicles (OM 6f 1T and 

BIB-4 
P.34 

8 Size Classes) report to the Engine Manufacturers Association, 

Chicago, IL. 

Tennyson, T.A* and CK . Parker (1970) "Locomotive Radioactive 

Ring Studies of Fuel, Lubricant, and Operating Variables", SAE 

Paper #700892, Society of Automotive Engineers, Warrendale, PA. 

Tupa, R. C and R.J. Dorer (1984) "Gasoline and Diesel Fuel 

Additives for Performance/Distribution/Quality", SAE Paper 

#841211, Society of Automotive Engineers, Warrendale, PA. 

Ullman, T.L., CT . Hare, and T.M. Baines (1983) "Heavy-Duty 

Diesel Emissions as a Function of Alternate Fuels", SAE Paper 

#830377, Society of Automotive Engineers, Warrendale, PA. 

(1984) "Influence of Maladjustment on 

Emissions from Two Heavy-Duty Diesel Bus Engines", SAE Paper 

#840416, Society of Automotive Engineers, Warrendale, PA. 

Ullman, T.L., CT . Hare, and CA . Harvey (1985) "Heavy-Duty 

Diesel Emissions from Operation on Crude and 

Minimally-Processed Shale Oils", SAE Paper #850270, Society of 

Automotive Engineers, Warrendale, PA. 

U.S. Environmental Protection Agency, Office of Mobile Source Air 

Pollution Gontrol (1979) "Draft Regulatory Analysis: Heavy-Duty 

Diesel Particulate Regulations", U.S. EPA, Ann Arbor, Michigan. 

Wade, W.R. and CM . Jones (1984) "Current and Future Light-Duty 

Diesel Engines and Their Fuels", SAE Paper #840105, Society of 

Automotive Engineers, Warrendale, PA. 

Wade, W.R., J.E. White, CJM. Jones, CE . Hunter, and S.P. Hansen 

(1984) "Combustion, Friction and Fuel Tolerance Improvements 

for the IDI Diesel Engine", SAE Paper #840515, Society of 

Automotive Engineers, Warrendale, PA. 

Wall, J.C and S.K. Hoekman (1984) "Fuel Composition Effects on 

Heavy-Duty Diesel Particulate Emissions", SAE Paper #841364, 

Society of Automotive Engineers, Warrendale, PA. 

Weaver, C (1984a) The Effects of Low-Lead and TTnleaded Fuels on 

flaanUn* Engines. Report under EPA Contract #68-01-6543, Energy 

and Resource Consultants, Boulder, CD. 

(1984b) "Particulate Control Technology and 

Particulate Standards for Heavy-Duty Diesel Engines", SAE Paper 

#840174 in Diesel Particulate Traps. P-l40, Society of 

Automotive Engineers, Warrendale, PA. 

Weaver, C , C Miller and L. Nel owe t (1984) Particulate Control 

Technology and Particulate Bniasions Standards for Heavy-Duty 

BIB-5 
P.35 

niesel Engines, report under EPA Contract 68-01-6543, Energy 

and Resource Consultants, Boulder, CO. 

weaver, C and C Miller (1983) Irap-Oxidiger Technology for 

Tight-Duty niesel Vehicles; Feasibility. Costs, and Present 

status, report under EPA Contract 68-01-6543, Energy and 

Resource Consultants, Boulder, CO. 

BIB-6