P.1 

OAR Box 1852 

Prepped by Keeia Richards 

Document Number: 

38) ll-C-14 

Docket Number: 

A-86-03 

Printed 11/19/2008 2:38:54 PM Sheet 38 of 101 
P.2 

'* ^ * \ UNITED STATES ENVIRONMENTAL PROTECTION AGEN 

ussy 

AUG 71987 

MEMORANDUM 

A-8<r--C>3 

DRAFT 

ANN ARBOR. MICHIGAN 48105 

H © H 0 w 

AUG - 9 1989 

OFFICE OF 

AIR ANO RADIATION 

^U iv j£it£ Qfl ent 

SUBJECT: Effect of Fuel Sulfur on Engine Wear/Engine Life 

FROM: 

TO: 

THRU: 

Timothy L. Sprik, Chemical Engineer 

Standards Development and Support Branch 

Charles L. Gray, Jr., Director 

Emission Control Technology Division 

Tom Darlington, Mechanical Engineer 'XHAA *3b\JcA~*(ftr\^ 

Standards Development and Support Branch J 

Richard A. Rykowski, Senior Project Manger 

Standards Development and S^*pportyBranch 

Chester J. France, Chief 

Standards Development an^/frupp, 

The purpose of this memo is to summarize the results of a 

study contracted to SwRI on the effect of fuel sulfur on engine 

wear and engine life. The draft report received from Southwest 

Research Institute took two approaches in analyzing the effect 

of sulfur on engine wear. The first approach was to analyze 

all available data in the literature investigating the 

relationship between engine wear and fuel sulfur content, 

operating conditions (load and speed), and engine temperature. 

The second approach was to evaluate oil analysis data obtained 

from diesel fleets operating in California's South Coast Air 

Basin (SCAB) before and after legislation reducing the sulfur 

content to 0.05 weight percent went into effect in January, 

1985. Comparison analysis of oil iron content before and after 

the imposed sulfur reduction was anticipated to give an 

indication of the impact of sulfur on wear under "real world" 

operating conditions. 
P.3 

-2-

Literature Search 

The literature search done by Southwest was more 

comprehensive than any previously undertaken in the area of 

sulfur and engine wear. However, most of the data relating 

sulfur to engine wear was old (1940's and 50's) and,^ due to the 

difference in oil qualities, past and present, cannot be 

applied quantifiably to current engines. Another limitation of 

most of the literature data is that the impact of sulfur on 

engine wear was addressed under carefully controlled steady 

state conditions, and not in-use transient conditions. 

One source in the literature which did take all of these 

parameters into account was the docket submittal of Mercedes 

Benz. Wear testing was performed on a Mercedes Benz 0M422 

engine (4 stroke, DI, naturally aspirated, 14.6 liter) 

operating on API CC 20 W 20 oil. The oil was changed 

frequently to retain resolution of the experimental measurement 

technique, and therefore there was no significant TBN 

depletion. The wear effects of fuels with sulfur levels of 

0.26 and 0.05 weight percent were investigated over a range of 

engine operating conditions (load, speed, temperature). 

Reduced corrosive wear was observed during conditions typical 

of cold start and warm-up conditions. For instance, at coolant 

temperatures of 122°F, an 80 percent reduction in bore wear was 

observed. At 158°F, the reduction was only 28 percent, and at 

176°F, there was no difference in the observed rates of wear 

for the different fuels. At even higher temperatures, the low 

sulfur fuel actually showed a slight increase in wear. 

Mercedes then developed a mathematical correlation of wear vs. 

engine operating, fuel, and oil parameters, which agreed well 

with the test data. Southwest did not, however, attempt to use 

this equation to determine the overall wear reduction which 

would be seen in engines under a variety of operating 

conditions. This exercise may be possible to perform in-house, 

however, in order to determine the impact of the rate of 

warm-up (as it relates to ambient temperatures) on wear in 

conjunction with the findings of the fleet oil analysis. 

The final conclusion of Southwest with regard to the 

literature search, however, was that the interrelationship of 

engine operation, fuel quality, oil alkalinity, and temperature 

was too complex, and that no quantification of the effect of 

fuel sulfur reduction on engine life was possible. 

Used Oil Analysis 

The investigation of Southwest into oil analysis data in 

the SCAB proved to be somewhat more fruitful. Four local 

southern California fleets were able to supply oil analyses 

from before and after the implementation of 0.05 sulfur 

legislation. The largest of these fleets was the South Coast 

Rapid Transit District (SCRTD), which operates 2500 transit 
P.4 

-3-

buses powered by Cummins, Detroit Diesel, and MAN engines. 

About 30,000 oil analysis records were available, from 1984 

(pre 0.05 sulfur) and 1985 and 1986 (post 0.05 sulfur), of 

which approximately 7000 were deleted due to suspected 

recording errors. Sulfur levels of the fuel were 0.35 wt. 

percent in 1984, and 0.03 (0.02) wt. percent in 1985 (86). 

Given these sulfur levels, an average 30 percent"reduction in 

oil iron content was seen between 1984 and 1985-86. 

It should be pointed out that, as expected, not all 

operating parameters were constant during this three year 

period. New oil TBN, a measure of the oil alkalinity, 

increased from 5.4 in 1984, to 7.4 (6.1) in 1985 (86). Used 

oil TBN values were 4.4, 5.8, and 6.0 respectively. From this 

parameter only, one would expect to see a decrease in corrosive 

wear rates in 1985-86, and therefore, the reduction in oil iron 

content could be partially attributable to this. Considering 

this, the wear rate reduction determined from the data will 

arguably be maximum. Also, current national fuel sulfur levels 

are around 0.25 wt. percent, and therefore, rules limiting 

sulfur content to 0.05 would only experience 62 percent of the 

sulfur reduction experienced in the SCRTD fuel. Adjustment to 

the results to incorporate this difference is also necessary. 

In spite of these problems, however, the primary advantage 

of the SCRTD fleet oil analysis data over experimental studies 

is that the oil analysis procedure measures total iron worn in 

the engine as opposed to measuring only ring and/or liner wear 

(as in the experimental studies). According to a 1981 EMA 

rebuild survey, loss of oil control is a major factor in 

deciding when an engine is rebuilt. This loss of oil control 

can come about through several mechanisms, including (1) 

abrasive wear of the cylinder from piston deposits, (2) ring 

scuffing from overfueling and overheating, (3) broken rings, 

and (4) corrosive wear. Fortunately, all of these wear 

mechanisms result in wear particles being deposited in the oil, 

and are therefore accounted for in the comparative oil iron 

analysis. The percentage reduction in oil iron content can 

therefore be directly related to a decrease in combustion 

chamber wear and, consequently, a decrease in oil consumption. 

Data from the other three SCAB fleets were less reliable 

since: 1) no fuel analysis data could be provided, 2) the 

number of samples were significantly less (a total of only 

about 2000 for the other three fleets combined as compared to 

about 30,000 for SCRTD), and 3) there was a significant 

increase in the levels of zinc present in the oil in 1985-86 

compared to 1984. Zinc dithiophosphate (ZDTP) is well 

established as an inhibitor to abrasive wear, and it is 

therefore difficult to determine the relative contributions of 

the zinc increase and the sulfur decrease to the reduction in 

wear observed. Southwest did conclude that they feel the zinc 

increase did not contribute significantly to the reduction in 
P.5 

-4-

wear, but this claim was not well supported and therefore the 

data from SCRTD should be considered preferentially. 

Considering all of the oil analysis data, however, 

Southwest did conclude that it appeared that a significant 

decrease in oil iron content was observed with „lower sulfur 

fuel. However, they felt that this reduction in wear could not 

be extrapolated to engine life, and therefore no quantitative 

statement about the effect of desulfurization on engine life 

was made. 

In summary, the Southwest report did not discuss 

adequately how to relate the findings of the literature search 

and oil analysis to engine life, and consequently left the 

issue unresolved. After conversation with the Southwest staff 

members responsible for the report and other members of 

industry familiar with the issue, however, an internal approach 

was developed for using the data to quantify potential 

increases in engine life. This is described generally in the 

following paragraphs, and an example calculation for buses is 

outlined in Appendix A. 

Internal Approach to Estimating Wear Benefits 

Our approach uses the fleet oil analysis data, with the 

primary issue being how to relate a percentage decrease in 

engine wear products (iron) to an increase in fleet lifetime 

VMT and, consequently, a savings to owners/operators. The 

first area of focus is to determine the actual reduction in 

wear rates. Since the bulk of the data is taken from 

two-stroke Detroit Diesel engines, many of the iron wear 

particles are lost due to the high oil consumption of these 

engines. In other words, the concentration of iron in the oil 

may not increase linearly with time, but may reach an 

"equilibrium" value where the rate of iron in equals the rate 

of iron lost in the consumed oil. The analysis was done two 

ways. One way was to compare absolute values of iron in the 

oil, independent of miles on the oil sample, and the other was 

to normalize iron content by the miles on the oil sample, 

giving "iron per mile" values. There was little difference in 

the final results between these two methods. Comparison of 

wear rates before and after the sulfur reduction were made, and 

a percentage reduction was determined. 

The next step was to translate this percentage reduction 

in wear rate to an extension in vehicle life. A rebuild survey 

done by EMA was obtained from which the fraction of rebuilds 

necessitated by loss of oil control, blowby, and poor oil 

analysis (all a function of cylinder wear) was estimated. The 

wear benefit was then applied to only those engines. Engines 

which failed for other reasons (see Appendix A) were assumed to 

receive no benefit. Vehicles removed from the fleet by crashes 

likewise received no benefit. These extensions in vehicle life 
P.6 

-5-

were then put in terms of a savings in owners' cost in terms of 

dollars per mile. For buses this resulted in an extension of 

about 6 percent in lifetime vehicle mileage, and a reduction in 

yearly operating costs of about $672 (1.50/mile or 80/gallon). 

It should be noted that the bulk of this cost benefit results 

from the fact that the life benefit is claimed on the entire 

vehicle chassis (=$150,000). Were the benefit claimed only 

on the engine (-$15,000), the savings would only be about 

$100 per year (^It/qzl). Other calculations are shown in the 

Appendix A. 

Probably the main question involved with this analysis is 

whether the SCRTD fleet data should also be used for HDD and 

LDD analysis. The majority of the SCRTD data is taken from DDA 

two-stroke enqines operating as transit buses, and may not be 

applicable to line-haul, medium duty, and light duty 

operation. Data from the other two California fleets (shown in 

Appendix B) show varying results. The rental truck fleet 

generally confirms the SCRTD results. The Chandler fleet shows 

an increase in oil iron content with lower sulfur, which we are 

currently attributing to the small sample size in 1984 versus 

1985 and 1986 or perhaps errors in analysis or reporting (since 

other samples are generally in good agreement). 

The reduction in line haul engine wear rates, however, 

would probably be different from that seen from buses. First 

one would expect to see higher average operating temperatures 

in line-haul engines, at which it appears that the effect of 

sulfur is much less. Also, at high temperature operation, 

formation of piston deposits increases, which would increase 

the rate of abrasive wear. A reduction in corrosive wear would 

therefore represent a smaller fraction of the total wear, and 

the overall effect of a sulfur reduction would be less. On the 

other hand, oil consumption in 4-stroke engines would be 

expected to be less than that seen on the 2-stroke engines 

investigated. Frequent replenishing of the 2-stroke engines 

oil supply, therefore, might insure that oil TBN never drops to 

critical levels. Pursuing this logic, it might be expected 

that 4-stroke engines operate on low TBN oil more frequently, 

and would therefore be more sensitive to the sulfur level in 

the fuel. 

Another factor which complicates the analysis is the fact 

that the ambient temperatures experienced by the SCRTD fleet 

are higher than those experienced by most diesels in the 

nation. Engines in colder climates may spend more time 

operating at low coolant temperatures where the corrosive 

problem is exacerbated. Hence, engines in colder climates may 

see a greater benefit from a fuel sulfur reduction than the 

SCRTD fleet. Clearly, the question of applicability of the 

SCRTD data to non-bus applications is complex. However, at 

this point, since the largest and most reliable data base of 

oil samples taken were from SCRTD buses, it has been 

preliminarily decided to use this data for all engines instead 

of data from the smaller fleets. 
P.7 

Appendix A: Extension of Engine Life 

Methodology of Calculations 

Analysis of SCRTD Data 

a. Assumptions 

i. The oil used in 1984, 1985, and 1986 was 

sufficiently alkaline (4.4 - 7.4 TBN) from one 

oil change to the next. Although average TBN 

increased in 85-86 by about l TBN, the levels 

were always within manufacturer recommended 

levels, and since it appears TBN operates on a 

"threshold" effect, it should not 

significantly affect the difference between 84 

and 85-86 wear levels. 

ii. The iron in the oil is all derived from the 

liner, rings, pistons, etc. SwRI agrees with 

this assumption. Any differences seen in the 

oil iron content represents a direct 

percentage reduction in cylinder liner, bore, 

and ring wear, which should correlate well 

with engine life. (If this assumption were 

false [i.e., < 100 percent of iron came from 

cylinder] then a percent reduction in iron 

between 1984 and 1985-86 would correspond to a 

greater percent reduction in cylinder wear, 

assuming that corrosive wear was the only 

difference between 1984 and 1985-86). 

iii. Oil consumption, on average, was the same all 

three years. 

iv. a) Iron wear normalized to oil miles 

assumes low oil consumption (i.e., 

little dilution by addition of fresh oil 

to the crankcase). 

b) Iron wear not normalized assumes high 

oil consumption (i.e., the iron level 

reaches an equilibrium value, where iron 

in = iron burned with consumed oil, and 

therefore does not change with mileage. 
P.8 

Percent Reduction in Iron Content Normalized to Oil 

Miles From SCRTD Data 

% of 

Samples 

0.77 

52.6 

45.6 

1.03 

Enqine 

CUV903 

DDV71 

DDV92 

MAN866 

Year 

84 

85 

86 

84 

85 

86 

84 

85 

86 

84 

85 

86 

Samples 

87 

73 

15 

2054 

5111 

4836 

458 

4387 

5551 

59 

67 

110 

Iron(pp 

(xlO1) 

6.277 

8.210 

6.899 

12.543 

8.835 

9.611 

^13.316 

8.051 

8.501 

14.343 

24.548 

24.013 

Iron(ppm)/Mile %Reduction 

(xlO1) Iron(ppm)/Mil 

-30.1 

- 9.9 

29 

23 

39 

36 

-71.2 

-67.4 

22808 

Adjust % Reduction to National Sulfur Level Change 

d. 

% of 

Samples 

52.6 

45.6 

e. 

Year 

1985 

1986 

Avg. 

% Red 

Iron(ppm)/Mile 

Percent Reduct 

(assuminq 

Engine 

DDV71 

DDV92 

Adjust % 

(high oil 

Year 

1985 

1986 

Avg. 

hiqh 

Year 

84 

85 

86 

84 

85 

86 

32.6 

28.0 

30.3 

ion in Iron 

% Red at 

0.238^-0.05 Sulfur 

19.2 

16.0 

17.7 

Content from SCRTD Data 

oil consumption on DDV71 and DDV92) 

Samples 

2054 

5111 

4836 

458 

4387 

5551 

Iron % 

(ppm) Reduced 

82.1 

63.6 22.5 

66.2 19.3 

82.1 

50.1 39.0 

51.6 37.2 

Reduction to National Sulfur Level Chanqe 

consumption) 

% Red 

Iron 

30.2 

27.6 

28.9 

% Red at 

0.238+0.05 Sulfur 

17.7 

15.7 

16.7 
P.9 

2; Application of cylinder wear reduction to engine life 

extension 

a. Fraction of rebuilds caused by ring & liner wear 

i. EMA rebuild criteria survey (fleet survey) 

Frequency of 

Reasons Cited % 

% 

Criteria 

Oil Consumption 

Maj Engine Failure 

Reduction in Oil Press. 

Blowby 

Loss of Performance/ 

Reduced Power 

Miles 

Oil Analysis 

Compression Pressure 

Engine Hrs. 

Years in use 

Total Responses 

Fraction of Engines not 

i. Vehicle Crashes 

of Fleets 

Citinq 

80 

65 

62 

57 

46 

32 

22 

18 

9 

6 

397 

rebuilt 

20.2 

14.4 

5.5 

40.1% 

(36.3%)* 

From MVMA facts and figures, 1986, assuming 

all vehicles not surviving year number one are 

totaled crashes, 

Crash Rate =0.3 percent per year HDD 

0.7 percent per year LDDT 

0.4 percent per year LDDV 

Owner Operator Survey 
P.10 

ii. Chassis Failure 

It was assumed that scrappage due to chassis 

failure was minimal, and since no data could 

be found concerning this, failure rate = zero. 

Operating Costs - Urban Bus 

Lifetime Mileage 

Miles/year 

Vehicle Life (yrs) 

Discount Rate 

Baseline 

540,000 

45,000 

12.0 

10% 

Discounted Lifetime Mileage 320,290 

Overhaul 

Mileage to 1st Overhaul 

Years of Operation 

Before Overhaul 

Fraction of Vehicles 

Purchased 

Removed by Crashes 

before 1st overhaul 

Cost of Overhaul ($) 

Present Value Cost of 

Overhaul($) 

Coach (w/Engine) Cost 

(new) ($) 

Total Present Cost 

Lifetime Operating Cost 

($/mile) 

Operating Cost Reduction 

($/yr) 

304,000 

6.76 

0.0203 

5,000.00 

2,571.87 

150,000 

152,571.87 

0.4764 

0.05 Sulfur : 

574,686* i 

45,000 i 

12.77 

10% 

330,399 

325,577 

7.24 

0.0217 

5,000.00 

2,453.35 

150,000 

152,453.35 

0.4614 

(-0.0149) 

672.01 

Assuming a 17.7 percent decrease in cylinder wear and 

accounting for additional vehicle crashes and vehicle 

failures due to non-oil-control-related reasons during the 

additional VMT for vehicles benefiting. 
P.1L 

-

1 

% of 

Fleet 

20.7 

31.7 

47.6 

2 

3 

% of 

% Red 

Fleet 

12.6 

50.1 

4.5 

0.8 

32.0 

4 

. 

Eng: 

Cat 

Appendix B: Data From 

Chandler 

m e 

Cummins 

DDA 

. 

• 

Yr 

84 

85 

86 

84 

85 

86 

84 

85 

86 

Summary: 

• Truck 

Samples 

6 

54 

82 

5 

74 

138 

22 

119 

185 

685 

Other SCAB Fleets 

Fleet Engines 

Iron 

(ppm) 

72.9 

78.2 

50.4 

9.8 

17.2 

21.6 

53.2 

55.5 

62.3 

Iron(ppm)/Mi 

(xl0J) 

24.57 

46.77 

48.5 

1.9 

3.8 

4.9 

13.3 

12.1 

14.7 

Chandler Fleet 

Year 

1985 

1986 

Avg. 

% Red 

Iron 

-27.5 

-39.9 

-33.7 

% Red 

Iron/Mile 

-46.1 

-75.2 

-60.7 

Rental Truck Fleet Engines 

Enqine 

Cummins 

DDA 

Deutz 

GMC 

I-H 

Yr 

84 

85 

86 

84 

85 

86 

84 

85 

86 

84 

85 

86 

84 

85 

86 

Summary: 

Samples 

38 

34 

51 

126 

162 

200 

8 

16 

20 

2 

2 

4 

90 

114 

108 

975 

Rent a 

Year 

1985 

1986 

Avg. 

Iron 

(ppm) 

34.8 

32.5 

37.3 

85.3 

62.9 

56.4 

128.3 

82.3 

102.1 

31.0 

18.0 

8.7 

72.0 

53.8 

49.3 

Iron(ppm)/Mi 

(xlO3) 

3.13 

2.76 

2.82 

10.7 

8.3 

6.7 

16.8 

9.7 

13.6 

4.4 

2.6 

1.5 

11.6 

9.0 

8.2 

1 Truck Fleet 

% Red 

Iron 

24.1 

27.6 

25.9 

% Red 

Iron/Miles 

22.1 

30.7 

26.4 

le % Red 

Iron 

-7.3 

30.9 

-75.5 

-120.4 

-4.3 

-17.1 

le % 

Iron I 

6.6 

-7.2 

26.3 

33.9 

35.9 

20.4 

41.9 

71.9 

25.3 

31.5 

% Red 

Iron/Mile 

-90.3 

-97.44 

-100 

-158 

9.0 

-10.5 

Red 

ron/Mile 

11.8 

9.9 

22.4 

37.4 

42.3 

19.0 

40.9 

65.9 

22.4 

29.3 
P.12 

1 

V 

AUG 7 1937 

Dear : 

Bnclosed for your review are copies of three reports which 

will play an important cole in our understanding of the costs 

and benefits of controlling the quality of on-highway diesel 

fuel. Please provide us with your comments oa the enclosed 

reports within the next thirty days, as we plan on 

incorporating the results of these reports in our study of 

diesel fuel quality to be published son*tiae this fall. 

The enclosed stuoy from Bonner * Moore Management Science 

is a draft report which shows the results of their nationwide 

refinery modeling. The acceiing was conducted to determine the 

nationwide refinery cost for controlling both diesel fuel 

sulfur content as weil as sulfur and aromatics, content 

simultaneously. We specifically request your consents in the 

following two areas: 1) The industries' ability to segregate 

on-highway diesel fuel from other distillate products, and 2) 

the estimates of the investments required to hydrotreat the 

controlled distillate pool voluaea. \ 

Also enclosed is the Southwest research Institute report 

entitled, "study of the affects of Reduced Diesel Fuel Sulfur 

Content on Engine Hear." The report suwaariaes the results of 

their literature search on the effect cf fuel sulfur on engine 

wear, and gives a sumcary cf the analysis of engine oils taken 

froa South Coast Air Basin (SCAB) fleets from both before and 

after fuel sulfur regulation. Thu report concludes that there 

appears to be a reduction in oil iron content coinciding with 

lower fuel sulfur levels. Please comment on the contents if 

this report, particularly the finuing of the oil analysis and 

the suamary and conclusions. 
P.13 

The third item is a memorandom describing a preliminary 

ec:tempt to apply the results cf the SCAB fleet oil analysis to 

the expected life ar.d costs associated with owning and 

operating urban transit buses. Please provide comments on the 

methodology used in this analysis, particularly with-respect to 

the relative contributions of corrosive and abrasive cylinder 

wear to loss of oil control, and the applicability of applying 

data taken from buses to line-haul engine operation. Thank you 

in advance for your cooperation. 

Sincerely yours, 

Charles L. Gr; _ 

Director 

Emission Control Technology Division 

Enclosures 
tam 

P.14 

|BBgiat{j 

Mr. Bruce I. Bertelsen 

MECA 

1001 Connecticut Avenue, N.W. 

Suite 830 

Washington, DC 20036 

Mr. Herbert W. Bruch 

Technical Director 

National Petroleum Refiners 

Suite 1000 

1899 L Street, NW 

Washington, DC 20036 

Association 

Mr. Marcel Halberestadt 

Motor Vehicle Manufacturers Association 

300 New Center Building 

Detroit, MI 48202 

Mr. Ronald L. Jones 

Refining Director 

American Petroleum Institute 

1220 L Street, NW 

Washington, DC 20005 

Mr. Chris Weaver 

Radian Corporation 

10395 Old Placerville Rd. 

Sacramento, CA 95827 

Mr. Thomas C. Young 

Executive Director 

Engine Manufacturers Association 

1 Illinois Center 

111 East Wacker Drive 

Chicago, IL 60601