P.1 

OAR Box 1856 

Prepped by Keeia Richards 

Document Number: 

69) ll-A-06 

Docket Number: 

A-87-11 

Printed 11/24/2008 12:41:50 PM Sheet 69 of 82 
Ami 

IJ. fi-Oie 

EPA-AA-SDSB-85-6 

Technical Report 

Refueling Emissions from Uncontrolled Vehicles 

By 

Dale Rothman 

and 

Robert Johnson 

NOTICE 

Reports do not necessarily represent final EPA 

or positions. They are intended to present 

analysis of issues using data which are 

available. The purpose in the release of such 

is to facilitate the exchange of technical 

Technical 

decisions 

technical 

currently 

reports 

information and to inform the public 

developments which may form the basis for 

decision, position or regulatory action. 

of 

a 

technical 

final EPA 

Standards Development and Support Branch 

Emission Control Technology Division 

Office of Mobile Sources 

Office of Air and Radiation 

U. S. Environmental Protection Agency 
Table of Contents 

Page No 

I. Background 1 

II. Parameters Affecting Refueling Emissions l 

A. Differences Between Vehicle Tank 

Temperature and Dispensed Fuel Temperature 

B. Dispensed Fuel Temperature 

C. Fuel Volatility (Reid Vapor Pressure) 

D. Vehicle Differences 

E. Other Factors 

III. Baseline Refueling Test Program 8 

A. Vehicles and Test Conditions 

B. Test Procedure 

1. Overview 

2. Effects of Vehicle Preconditioning 

C. Test Results 

1. Summary 

2. Parameter Effects 

a. Differences Between Vehicle 

Tank Temperature and Dispensed 

Fuel Temperature 

b. Dispensed Fuel Temperature 

c. Fuel Volatility (Reid Vapor 

Pressure) 

d. Other Parameters 

3. Differences in Vehicles and Vehicle 

Configuration 

4. Prediction Equation 

a. Fitted Model 

1. Coefficients 

2. Variabilty 

b. Comparisons to Results from 

Other Studies 

IV. Calculation of Nationwide Emission Factors 38 

A. Introduction 

B. Description of Refueling Emission Factors 

C. Calculation of Displacement Emission Factors 

1. Methodology 

2. Sources of Data 

3. Air Quality and Health Effects Scenarios 

4. Consumption Weighting Calculation 

5. Emission Rates 

6. Effects of Fuel Weathering 

D. Conclusions 
P.4 

I. Background 

The Environmental Protection Agency is currently in the 

process of developing and evaluating a Federal test procedure 

for the measurement of vehicle refueling emissions. Refueling 

emissions are of direct concern due to their benzene content 

and the potential health effects of exposure to gasoline vapors 

in general. Also, they contribute to ozone formation, and are 

of particular concern in areas which currently do not meet the 

National Ambient Air Quality Standards (NAAQS) for ozone. 

This report describes EPA's baseline program to measure 

refueling emissions from uncontrolled vehicles, and to 

investigate the sensitivity of these emissions to various 

parameters. An emission factor equation based upon the various 

parameters will be developed that will be used in making 

comparisons with the results of other refueling emissions 

studies. It will then be used to estimate emission factors 

under a range of conditions. 

II. Parameters Affecting Refueling Emissions 

As was described by Hochhauser and Campion, the generation 

of refueling emissions . is a complex process "involving 

non-equilibrium, unsteady state interphase heat and mass 

transfer in a system where the mode of contact between gas and 

liquid cannot be easily defined or modeled."[1] It has been 

shown, however, that fairly good estimates of refueling 

emissions can be obtained from empirical equations based upon a 

few, easy to determine parameters.[1,2,3] Those parameters 

that appear to explain the most variability are: 1) the 

difference between the temperature of the dispensed fuel and 

the tank fuel, 2) the temperature of the dispensed fuel, and 3) 

the fuel volatility. Differences in the physical configuration 

of vehicles' fuel tanks and fill necks can also affect 

refueling emissions, but this is a variable that can not be 

easily quantified. A more complete description of each of 

these and other parameters considered is given in the following 

sections. 

A. Differences Between Vehicle Tank Temperature and 

Dispensed Fuel Temperature 

A major factor in determining the level of refueling 

emissions is AT, the difference between the temperature of 

the fuel in the vehicle tank and the dispensed fuel 

temperature.. The addition of fuel that is. warmer than the fuel 

in the vehicle tank in turn warms the tank fuel and vapor 

space, resulting in the vaporization of additional gasoline and 

expansion of the vapor mixture. This condition is known as 
P.5 

-2-

vapor growth. On the other hand, addition of colder fuel to a 

warmer tank cools the fuel in the tank and some of the vapor 

present is condensed into liquid. This condition is known as 

vapor shrinkage. When both fuels are at the same temperature 

(AT = 0) neither vapor growth no vapor shrinkage occurs and 

the volumetric refueling losses are almost identical to the 

amount of vapor displaced by the incoming gasoline. 

Nearly every previous study dealing with vehicle refueling 

emissions has recognized the importance of the relationship 

between AT and total refueling emissions.[1,2,4,5,6,7,8,9,10, 

11,12] This effect is generally expressed as changes in the 

ratio of either the volume of vapor displaced, or grams of HC 

emitted, to the gallons of fuel dispensed. In all cases, an 

inverse relationship between AT and volumetric refueling 

emissions has been seen as is illustrated in Figure l taken 

from a study by the Stanford Research Institute. In general, 

the same result holds for the mass of refueling emissions. 

However, due to the changing constituents of the vapor, at 

larger negative values of AT a positive relationship between 

AT and mass emissions results.[1,2,3,6,9] This "turning 

over" effect is shown in Figure 2, also taken from the SRI 

study. 

B. Dispensed Fuel Temperature 

The temperature of the dispensed fuel (T0) can exert a 

distinct impact upon refueling emissions, separate from its use 

in the determination of AT. It has long been known that the 

amount of vaporization of gasoline varies directly with 

temperature. This is the reason that mixture enrichment 

devices are required for cold starting. All other factors 

being equal, emissions would therefore be lower at colder 

dispensed temperatures, since less fuel would be vaporized.* 

Several of the previous studies have considered the effect 

of dispensed temperature upon refueling emissions.[1,2,3,4,6] 

In several of these, the value of AT is not separately 

computed and controlled, so it is difficult to separate the 

distinct effects that the dispensed fuel temperature has on 

refueling emissions from its role in vapor growth or 

shrinkage. Figures 3 and 4, however, show the effect of 

dispensed fuel temperature, when AT is also accounted for, as 

seen in two of the previous studies.[1,6] 

*It is interesting to note that this will not be the case 

for the temperature of the tank fuel (TT). Lowering 

TT at a constant T0 will create lower values of AT, 

resulting in vapor growth and increased emissions. 
- 3 -

P.6 

-30 - « 

INITIAL TANK TEMPERATURE MINUS 0ISPENSE0 PUEL TEMPERATURE — ~r 

SA-J750-J, 

FIGURE 1 VAPOR-LIQUIO VOLUME RATIO VERSUS INITIAL AT 

Source: Stanford Research Institute (9) 
- 4 -

P.7 

-10 - » 

INITIAL 

TANK TEMPERATURE MINUS 0. 

SPENSED FUEL TEMPERATURE - '"• ^.p.,,, , 

Sour c . : Stanford R.searc* Institute d ^ 
P.8 

EFFECT OF DISPENSED TEMPERATURE 

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. 7S Gas-6 Part II, August 15,i*'=>. 

Source: EPA ^por t 75-Gas b 

bj Scott Environmental (6) 

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-6-

C. Fuel Volatility (Reid Vapor Pressure) 

RVP is a measure of "front-end" volatility, or the ease of 

vaporization of gasoline at 100°F; the higher the RVP the 

greater the vaporization potential. Refueling events occur near 

this temperature, therefore refueling emission rates should 

vary with RVP; all other factors being equal, higher RVP fuel 

yielding higher emissions. 

In many of the previous studies, the RVP of the fuel, its 

effect being recognized, was held constant. Other studies have 

attempted to explore the relationship between RVP and refueling 

emissions in a quantitative fashion.[1,2,4,6,9] Figures 5 and 

6 show characteristic increases in refueling emissions at a 

higher RVP.[1,6] This relationship is also noted in other 

studies. 

A few studies have also considered the effect of 

dispensing a fuel of one RVP into a tank with residual fuel of 

a different, lower RVP.[3,9] The general result is larger 

vapor growth as a result of the dispensed fuel vaporizing to 

increase the hydrocarbon concentration in the tank to the 

higher vapor pressure of the dispensed fuel. 

D. Vehicle Differences 

As with any type of emissions, there will be differences 

in results from different vehicles. In the case of refueling 

emissions, these differences are primarily related to the 

vehicle's fuel tank system. 

Fuel tanks vary in size, shape, position of the fillpipe 

(i.e., rear fill or side fill), fill neck design, and internal 

baffling. Differences in the areas of the evaporative 

surfaces, effective height of the fillpipe over the evaporative 

surface and turbulent interactions between the entering fuel 

and existing vapors are among the most likely causes for the 

differences that are observed in refueling emissions between 

vehicles. 

Few of the previous studies on vehicle refueling, emissions 

have specifically addressed the issue of differences between 

vehicles in.terms of emissions. This is due predominantly to 

the fact that most of these studies were concerned with the 

efficiency of various control strategies, and the percentage of 

vapor recovered was of more interest than total emissions. 

Still, Scott Environmental Technology noted the strong vehicle 

effect on refueling emissions as evidenced by the increased 

variability in their results as larger numbers of different 

type vehicles were used.[6] Stanford Research Institute has 
P.10 

EFFECT OF FUEL VOLATILITY 

a 

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Source: EPA Report #D-« -

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noted not only changes in emissions between vehicles, but also 

a change- in the shape of the regression line relating refueling 

losses to AT.[9] Also, Exxon Research and Engineering has 

found average losses at the same test conditions ranging from 

4.5 to 5.4 gm/gal depending on the vehicle.[13] Thus, although 

the previous studies have not specifically addressed the issue 

of differences between vehicles, its effect has been noted. 

E. Other Factors 

Several other factors that may have an effect upon 

refueling emissions have been considered in previous studies. 

Among these are: fill rate, [1,9] amount of residual fuel in 

the tank,[3,9] total amount of fill,[1,3,9] position of nozzle 

in the fill-neck,[9] and ambient temperature.[3,8,9] The 

magnitude of these effects is much less than that for any of 

the factors described previously. Therefore, this study has 

been designed primarily to determine the effects of AT, 

dispensed temperature, and fuel volatility; and any insights 

that can be obtained about these other effects or differences 

between vehicles, will be secondary. 

III. Baseline Refueling Test Program 

A. Vehicles and Test Conditions 

Eight vehicles in all have been tested in the baseline 

program. These consist of six light-duty gasoline vehicles and 

two light-duty gasoline trucks. The tank sizes vary from 

vehicle to vehicle, as do the configurations of the tanks and 

their internal baffling. A listing of the vehicles is given in 

Table 1. 

The majority of the testing was performed on the 1983 

Cutlass Supreme, as it was the first vehicle tested. The 

matrix of parameter conditions under which the Cutlass was 

tested is shown in Table 2, along with similar but less 

extensive matrices for the 1984 Escort and the 1983 Reliant. 

The testing of these vehicles at the various parameter 

conditions allows for a more complete comparison of the 

differences in refueling emissions between vehicles. Of 

particular interest here is the difference in refueling 

emissions between side-fill and rear-fill vehicles. Of all the 

vehicles tested, only the 1983 Cutlass Supreme is a rear-fill 

vehicle, and the future fleet is expected to be dominated by 

side-fill vehicles. 

The remaining vehicles were tested primarily at one set of 

parameter conditions. By testing several vehicles, an 

indication of the range of refueling emission rates can be 

obtained. 
-9-

P.12 

Table 1 

Year Make/Model 

1983 

1983 

1984 

1984 

1983 

1983 

1979 

vehicles Tested 

Tank Vol 

Olds. Cutlass Supreme 

Buick Skylark 

Chevrolet Celebrity 

Ford Escort 

LDT Crown Victoria 

Plymouth Reliant 

x,,, Dodge Truck W150 

1979 Chevrolet 3/4 Ton 

Pickup 

18. 

14. 

16. 

13. 

18 

13 

18 

1 

5 

4 

.0 

.0 

.0 

.0 

19.6 

Comments 

Rear fill 

Fuel Injected 

Vertical Tank 
P.13 

-10-

Table 2 

Refueling Emissions Test Matrix 

1983 Oldsmobile Cutlass 

Fuel Dispensed Temperature Tank Temperature 

80, 92, 100, 120°F 

80, 92, 100, 120°F 

80, 92, 100, 120°F 

80, 92, 100, 120°F 

80, 92, 100°F 

80, 92, 100°F 

1984 Ford Escort 

Fuel Dispensed Temperature Tank Temperature 

9.0 RVP 

11.9 RVP 

10.0 RVP 

12.6 RVP 

82°F 

92°F 

82°F 

92°F 

92°F 

82°F 

9.0 RVP 

11.9 RVP 

80°F 

92°F 

66°F 

80'F 

92°F 

82, 92, 

92°F 

72°F 

82, 92, 

92°F 

100°F 

100°F 

1983 Plymouth Reliant 

Fuel Dispensed Temperature TanK Temperature 

9.0 RVP 66°F 72°F 

11.9 RVP 66°F 72°F 

80°F 82, 92, 100°F 

92°F 92°F 

Remaining Vehicles 

Fuel Dispensed Temperature Tank Temperature 

11.9 RVP 80, 92°F 92°F ' 
-11-

P.14 

B. Test Procedure 

1. Overview 

The refueling emissions tests were performed in the manner 

outlined in Table 3. The test vehicle was pushed into the 

Sealed Housing for Evaporative Determination (SHED) "cold", 

i.e., at ambient temperature. At this point there was a 10 

percent fill in the tank. The vehicle's fuel tank was then 

heated, either by a single or dual heating blankets, to the 

desired temperature, inside the open SHED.* 

operating inside the SHED during this time. e 

had generally been heated to its desired temperature previously. 

The purge fan was 

The dispensed fuel 

At the end of the heating phase, the heating blankets were 

unplugged, the fuel nozzle was inserted into the fuel neck, the 

mixing fans were started, and the SHED was sealed. A 

background reading was then taken inside the sealed SHED before 

the refueling began. The refueling was then performed by 

turning on the fuel cart from outside the SHED. The refueling 

ended at a 95 percent fill, either when the nozzle had 

automatically shut off, or when it was shut off manually 

outside the SHED. The first method led to some problems with 

spillage, so in the later testing only manual shutoff was used. 

Temperature sensors were located at three points inside 

the tank, in the fuel cart, and at various other places in the 

testing setup, and values were recorded approximately every two 

minutes throughout the test. The measurements of refueling 

emissions were made with the use of a Flame Ionization 

Detection device. 

2. Effects of Vehicle Preconditioning 

As was described in the previous section detailing the 

test conditions, the vehicle's fuel tanks were heated either by 

single or dual blankets. The earliest tests on the 1983 

Cutlass were the only ones where a single blanket was used. 

Heating of the fuel tank was done with the general constraint 

that vapor and liquid temperatures not be allowed to differ by 

more than 6°F. Under these conditions, the time required to 

heat the tank to the desired temperature was in many cases 

excessive, i.e., an average of three hours to reach a tank 

temperature of 1Q0°F. Also, since the tank was only heated 

from below, temperature stratification occurred inside the tank, 

In a few of the tests the vehicle was driven on a road 

circuit before the refueling, heating the vehicle's fuel 

tank in the process. 
P.15 

-12-

Table 3 

Tost Sequence 

l Drain and refuel tan.- 10 percent of fuel capacity. 

J; Push vehicle int£ shed thecmocouples^ 

3. connect heat Dl«*« d temperature, 

A Heat vehicle tan* to 

*' msert fuel nozzle. , 

^'"shsd f d start mixing an n „D,. 

*, TaKe i""al sample ceadi n |L^ clty i 

\\\ Remove vehicle from shed. 
P.16 

-13-

with the . vapor temperature 

temperature by several degrees. 

was unclear as to whether an 

vehicle's fuel tank. 

lagging behind the liquid 

At the time of refueling, it 

equilibrium existed in the 

The use of dual heating blankets (the second blanket being 

used to heat the top of the fuel tank) drastically reduced the 

heating time required, and alleviated the problem of 

temperature stratification in the fuel tank. This approach was 

therefore adopted as the standard tank heating procedure. 

Figures 7, 8, and 9 show the results of the refueling 

tests for various methods of vehicle preconditioning. These 

data are solely from tests on the 1983 Cutlass, at a constant 

RVP and dispensed temperature in each case. Figure 7 gives a 

comparison of the results when the vehicle was heated by a 

single blanket, heated by dual blankets, or driven on a road 

circuit. Figure 8 shows further results when the vehicle was 

heated by dual blankets compared to when it was driven on a 

road circuit. Finally, Figure 9 shows the results of tests in 

which the vapor and fuel temperatures inside the vehicle's fuel 

tank were permitted to differ markedly. 

Several conclusions can be drawn from these test results. 

Refueling emissions were lower by approximately 0.7 gm/gal when 

under single blanket heating versus dual blanket heating. 

Large differences in the fuel tank liquid and vapor 

temperatures may affect refueling emissions, with lower 

emissions resulting when the vapor temperature lags behind the 

liquid temperature. The results from the road circuit tests 

appear to fit better with the single blanket tests, but half of 

these also fit with the dual blanket tests fairly well.** 

It is unclear how much of the difference between the 

single and dual blanket test results can be explained by the 

temperature stratification in the vehicle's fuel tank, and what 

must be explained by other factors. Because of its heating 

time advantages, and the question of tank equilibrium, dual 

blanket heating was used in the actual baseline testing. The 

results from the tests on the vehicle prepared on the road 

circuit, which are taken to represent a real-life situation, 

suggest that the dual blanket heating procedure may yield 

slightly conservative, but generally accurate, estimates of 

refueling emissions in real life situations. 

** When 90 percent confidence intervals for the regression 

lines are used. 
P.17 

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C. Test Results 

1. Summary 

It has been found that the refueling emissions, in grams 

of HC per gallon of fuel dispensed, can be estimated accurately 

by a multiple linear regression model relating refueling 

emissions to the difference between vehicle tank temperature 

and dispensed fuel temperature (AT), the dispensed fuel 

temperature, and the fuel volatility. The effects of vehicle 

configuration were explored and found to be of some 

significance.* The following general conclusions can be 

reached from the results. 

a) lower tank temperatures, relative to the dispensed 

fuel temperature, yield higher emissions, 

b) higher dispensed temperatures yield higher emissions, 

c) higher RVP dispensed fuel yields higher emissions; 

and, 

d) vehicle configuration can have a significant impact 

on refueling emissions. 

A more detailed look at each of these factors follows. 

2. Parameter Effects 

a. Differences Between Vehicle Tank Temperature and 

Dispensed Fuel Temperature 

Due to the phenomena of vapor shrinkage and vapor growth 

the difference between the tank temperature and the dispensed 

fuel temperature has a significant impact upon refueling 

emissions. This difference is defined herein as TT - T0 

and will be referred to as AT. The tank temperature, TT, 

is measured as the liquid temperature in the vehicle fuel tank. 

Figure 10 shows a plot of refueling emissions against 

AT. The general trend of higher emissions at ' lower AT 

values, representing more vapor growth, is apparent even when 

other factors such as dispensed temperature and fuel volatility 

are not considered. Very few tests were run at negative values 

of AT, and none below AT= -12, so the turnover in the 

The results of all of the valid tests performed on each 

vehicle are summarized in Appendix A. This includes the 

special tests run on the Cutlass in addition to the 

primary baseline testing. 
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relationship between AT and mass emissions noted earlier from 

other studies is not seen here. 

b. Dispensed Fuel Temperature 

Figures 11 and 12 illustrate the effect that the dispensed 

fuel temperature can have upon refueling emissions. These 

plots are separated by fuel volatility, and the refueling 

emissions values are plotted against AT in order that the 

effects of dispensed temperature can be separated from these 

other parameters. The values plotted at each AT are the mean 

responses, along with the standard deviation of the observed 

test results (where applicable) for a range of ATs centered 

at that point. A smaller standard deviation at a given point 

in these plots will not necessarily mean a more precise point, 

as the same number of tests were not performed at each point. 

They are presented here solely to give an indication of the 

variation in the test results. 

The figures indicate in general that higher dispensed 

temperatures will yield higher refueling emissions. This is 

especially true at values of AT around 0F° where a 10°F 

change in TD produces a 1 gm/gal change in emissions, with 

the effect being less notable at higher values of AT, where 

all values tend to converge. These results are consistent with 

those seen in previous studies. 

c. Fuel Volatility (Reid Vapor Pressure) 

Figures 13 and 14 illustrate the effect that the fuel 

volatility can have upon refueling emissions. The form of 

these plots is the same as in those used to illustrate the 

effect of dispensed fuel temperature, only here the dispensed 

fuel temperature is held constant as opposed to the fuel 

volatility being fixed previously. 

These figures give a clear indication that a higher fuel 

volatility, denoted by a higher RVP, will yield higher 

refueling emissions, as was seen in other studies. As with the 

dispensed fuel temperature, this effect is more noticeable at 

low values of AT. 

Several tests were run where a fuel with a lower 

volatility than the dispensed fuel was placed in the vehicle's 

fuel tank. This represents the case in which a vehicle's fuel 

weathers and loses some of its volatility between refuelings. 

The expected result, as described in the SRI study, is higher 

emissions resulting from vaporization of the dispensed fuel to 

increase the hydrocarbon concentration in the fuel tank to the 

higher vapor pressure at the dispensed fuel. The results from 

these tests are shown in Figure 14 as the three single points*, 

and reaffirm the results in the SRI study.[2] 
P.22 

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P.23 

-20 -

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-21-

d. Other Parameters 

It has been suggested that other parameters, such as 

ambient temperature and fuel dispensing rate may influence 

refueling emissions. In this particular testing program, it 

appears that the time required to heat the vehicle's fuel tank 

and the dispensing rate of the fuel may be of some 

significance. The design of this program, however, has made 

any significant analysis of these effects virtually 

impossible. Thus, although the presence of these effects are 

recognized, they cannot be determined here. Also, in 

comparison to the effects due to AT, the dispensed fuel 

temperature, fuel volatility, and vehicle configuration 

(discussed in the next section), these other effects are of 

much lesser significance. 

3. Differences in Vehicles and Vehicle Configuration 

For most of the vehicles tested, there is insufficient 

data to do independent parameter analyses. Therefore, a 

multiple linear regression has been fit using all of the data, 

and the residuals, the actual values minus the values predicted 

by the regression equation, have been examined.. The different 

patterns in the residuals from vehicle to vehicle can give an 

indication of the vehicle effects. Figures 15-22 show the 

residuals plotted against the predicted values for each vehicle 

individually, all plotted at the same scale. 

Of particular interest in these residual plots are the 

residuals associated with the LTD Crown Victoria, the Escort, 

and the Reliant. The residuals associated with the LTD are 

quite extreme, higher than those associated with any of the 

other vehicles aside from a few tests on the 1983 Cutlass. 

This may be due to the LDT's unique fuel tank configuration; 

its height dimension being larger than its width, with almost 

no drop in the fill neck. This configuration is atypical of 

the automotive fleet, and the results from the tests on the LTD 

would skew the prediction equation derived from the multiple 

linear regression model. Thus, although the LTD shows the 

potential range in refueling emission rates, its test results 

have not been used in formulating the prediction equation to be 

used here. 

The results are also listed in Appendix A under the 

heading Fuel Weathering Tests. 
' 

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1983 Olds. Cutlass Supreme 

• • • . ." • • * * 

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predicte d (gm/gal) 

, 

1983 LTD Crown Victoria 

; 

Predicted (gm/gal) 

FIGURES 15-18 

-22 -

t.f » • 

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1984 Ford Escort 

• • • 

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mm t.rrn ^^ t.mm , a ^ t.tlTf 

Predicted (gm/gal) 

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RESIDUAL PLOTS BY VEHICLE 

P.25 

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-24-

The residual plots associated with the Escort and Reliant 

both show a distinct pattern of underestimation of refueling 

losses (positive residuals) at low predicted values, and 

overestimation of higher predicted values. This would indicate 

that the fitted model here, dominated by data from the 

rear-filled 1983 Cutlass, may not be the most accurate for 

other vehicles, particularly side-filled vehicles which have a 

large vertical drop in the fill neck. 

A further comparison can be made by fitting a multiple 

linear regression model, based upon the same parameters as 

discussed before, for the Cutlass test results and for the 

Escort test results. These are the only two vehicles that have 

large enough data bases to make reasonable parameter 

estimates. The resulting fitted models are as follows: 

Cutlass: Refueling Loss (gm/gal) = 

-5.584 - 0.114[AT(°F)] + 0.0857[To(°F)] + 0.520[RVP(psi)] 

R

2

 = 0.856 

Escort: 

-6.68 

Refueling Loss (g 

17 - 0.039[AT(°F)] 

R

2

 = 0.912 

(gm/gal) = 

0.081[TD(°F)] 0.545[RVP(psi)l 

The resulting equation indicates that the primary differences 

in refueling emission between these vehicles lies in the amount 

of vapor shrinkage or vapor growth that occurs during the 

refueling event. These processes would naturally be related to 

vehicle configuration, so this result appears reasonable. 

A few more insights can be gained from an examination of 

the residual plots. Aside from the Celebrity whose residuals 

are consistently negative, although not as extreme as those for 

the LTD, the residuals for all vehicles generally fall within 

+ 1 gm/gal. This includes the test results from the two lightduty trucks which agree well with the prediction equation, even 

though it is based primarily upon automobile tests. 

In summary, it is clear that differences do exist from 

vehicle to vehicle. Nevertheless, an equation based upon all 

of the data, except the LTD tests for reasons as noted before, 

appears to work well on average. 

4. Prediction Equation 

a. Fitted Model 

A primary goal of this study has been to develop an 

emission factor equation based upon the parameters that affect 

refueling emissions. This has been achieved by fitting a 
-25-

multiple linear regression model with the data from seven of 

the eight vehicles tested.* 

The prediction equation developed for refueling emissions 

from an uncontrolled vehicle is given as follows: 

Refueling Loss (gm/gal) = 

-5.909 - 0.0949[AT(°F)] + 0.0884[TD(°F)] + 0.485[RVP(psi)] 

R

2 * 0.786 

MSE = 0.732 

This equation will be used to estimate emission factors 

under a range of conditions, and also will be compared with 

results from other refueling emission studies. The range of 

conditions over which actual tests were made is given below: 

T0 

To 

To 

1. 

66-68°F; RVP » 9.0-11.9 psi; AT 

78-858F; RVP = 9.0-12.6 psi; AT 

88-95°F; RVP = 9.0-11.9 psi; AT 

Coefficients 

0 to 10°F 

-2 to 40F° 

-12 to 32F° 

Each of the parameters included in the regression model is 

statistically significant at a confidence of 99.9 percent, 

i.e., there is less than a 0.1 percent probability that any of 

the three parameters has no effect upon refueling emissions. 

The magnitude of the effects due to each parameter is given by 

the associated coefficient in the regression equation. A 10F° 

increase in AT will lower refueling emissions by nearly 1 

gm/gal; a 10°F increase in TD will increase refueling 

emissions nearly l gm/gal; and a 1 psi increase in RVP will 

increase refueling emissions nearly 0.5 gm/gal. 

There was some consideration as to whether a linear model 

is sufficient to explain the data over the range of conditions 

where the regression equation is applicable. A look at the 

residuals (actual gm/gal minus predicted gm/gal) can give an 

indication as to whether the assumption of linearity is 

appropriate. Figures 23-26 show the residuals plotted against 

the predicted values and against each independent parameter. 

The residual scatter in these plots appears random, and no 

systematic trends are evident, which would indicate significant 

nonlinearity. Also, several other forms of the regression were 

considered in which interaction and nonlinear terms were 

included. These are presented in Table 4, along with the 

associated R*. The R" value is a measure, of a model's 

Does not include testing on the LTD or the special tests 

on the 1983 Cutlass (single blanket, etc.) 
-26 -

Table 4 

AlternativeJ^rmi^tions 

of Regression Model 

R

2 

P.29 

Gm/Gal = 

1) exp [a0+al(TT)+az(RVP)+a,(To)(TT)+ 

ay(T0)(RVP)] 

2) exp [ao+al(TT)+a,(T0)+ 

a,(RVP)] 

3) a0+ai(TD)+a,(TD)(TT)+ 

a,(Ti)(Ti) 

4) a,+ai(AT)+a,(AT2)+a,(T0)+ 

ay(RVP) 

5) ao+ai(AT)+a2(T0)+ 

a,(RVP) 

805 

.823 

.613 

.790 

.786 
2.5000 

7.0000 

I.5000 

I.0000 

h .60000 

K -.24564-14* 

. 50000 

-1.0000 • 

RESIDUAL VALUES vs. PREU.CTEO VALUES 

Fitted Mode. All Vehicles 

• • • • • • • 

• • • • 

• . 

I 

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I 

-».500 0 

i uuou 

2.UOOO 3 . 77/ B 5.555 6 

7.3333 

-r~*~" s.m i 

2 .6BB9 4.666 7 

6.444 4 

8222 2 10.000 

PREDICTED (gm/gal) 
P.31 

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RESIDUAL VALUES vs . DISPENSED TEMPERATURE 

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» 

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a.500 0 

10.00 0 

FUEL VOLATILITY 

2 

• 

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P.34 

l i -

ability to. predict trends that are presented in the data. 

These results show that the linear model is sufficient to model 

the baseline refueling data, and its simpler form makes it 

easier to interpret. 

2. Variability 

There is a large amount of variability in the results from 

the refueling emission tests; values ranged from under 3.0 

gm/gal to over 11.0 gm/gal. Nearly 80 percent of this 

variation is explained by the three parameters: T0, AT, 

and RVP, as indicated by the R2 value associated with the 

regression model. However, a fair amount of variability 

remains unexplained as shown by the mean squared error value of 

0.557 gm/gal. 

Much of the remaining variability is due to the 

differences in vehicles as discussed before, but other factors 

are also involved. Several parts of the test procedure are 

subject to certain degrees of error, and can therefore lead to 

test variability. The first of these involves the heating of 

the fuel tank in the vehicle as mentioned before. What effect 

the heating rate may have is unclear. The same can also be 

stated for the dispensing rate of the fuel. The heating of the 

dispensed fuel in the fuel cart also varies somewhat, and could 

very possibly slightly affect the RVP of the fuel. 

All of the above effects are generally negligible, 

however, in comparison to the effects caused by even a small 

fuel spill or spitback at the end of a refueling. Tests in 

which spills estimated at over 1/2 of a cup occurred were 

generally voided, except where no significant effect was 

noted. However, even a spill as small as 1 1/2 tablespoon 

could generate a one gram per gallon increase in emissions if 

it were to completely evaporate.* The concern over spills was 

large enough to change the test procedure used in this program 

to call for manual shutoff of the dispensed fuel. Also, the 

effect is large enough to warrant being considered in 

determining the total emission factor. This will be discussed 

more in the sections dealing with the refueling emission factor. 

b. Comparisons to Results from Other Studies 

The prediction equation derived here can be: 1) used to 

make comparisons with the results measured from other studies, 

and 2) compared to prediction equations derived elsewhere. A 

brief summary of the results from other studies, and how they 

compare to those in this study, is given in Table 5. Overall 

the results of this study are in good agreement with past work. 

Using 10 grams/tablespoon and assuming a 15 gallon refueling. 
P.35 

Summa 

-32-

Table 5 

ofj^lt s from Previous Studies 

Comments & Relation 

Study To('°F) AT(°F) RVP(psi) to Current Study 

Scott 55-70 -30 to 30 8.8, 12.0 Laboratory 

study;(lab)si milar 

effects seen 

for RVP, To, 

and AT; 

resulting gm/gal 

0-0.S gm/gaI 

lower 

1S75 Scott 80-85 -20 to 30 8.0-8.8 Field study of 4 

(station) Stage II 

Recovery Systems 

on vehicles at a 

service station 

; some base Iine 

testing done; 

mean values from 

baseline results 

agree weiI wi th 

predictions from 

this study. 

1S75 CAPE9 30-90 -40 to 40 7-13 Performed in 

SCOTT mini-shed 

on veh i cIe 

tanks; no tests 

of positive 

ATs at higher 

T0s; can only 

compare with 

current study at 

around AT=0F°; 

agreement is 

good in this 

range. 
P.36 

-33-

Table 5 (cont'd) 

Summary of Results from Previous Studies 

Comments & Relation 

Year Study T0(°F) AT(°F) RVP(psi) to Current 

Study 

1975 SRI 68-85 -30 to 45 6.9-8.6(10.6) Tests at a 

station on a 

vehicle fuel 

tank; 

comprehensive 

tests looking at 

many independent 

variables that 

affect refueling 

emissions; good 

general agreement 

with current 

study; slightly 

low at low ATs 

and higher at 

high ATs. 

1976 ER&E 10-100 -20 to 10 7-13 Fuel tank tested 

in control led 

envi ronment; 

vapors collected 

in Tedlar bag; 

yields results 

1-1.5 gm/gal 

lower at 0° AT, 

nearly equal at 

10° AT. 

1976 Union 75-85 -20 to 30 8.8-9.0 Tested random 

vehicles at a 

refueling 

station; 29 used 

for base Iine 

results; 

estimates 1 

gm/gal lower at 

0° AT, 

approximately 

equal at AT 10° 
P.37 

Summary 

-34-

Table 5 (cont'd) 

ofpo^lts from Previous Studies 

Year 

1978 

Study 

ER&E 

1978 Mobi I 

T0(°F) Ali!f) 

85 

82-85 

-1 

RVP(psi) 

9.1 

Comments & Relation 

to Current Study 

Looking at 

efficiency of an 

onboard control 

system on 3 

vehicles. 

Baseline 

est imates .7-1.6 

gm/gal lower 

than predicted 

by current study. 

8.2-12.0 Tests on a 

single vehicle. 

Good agreement 

with predicitons 

from current 

study. 
-35-

In order to estimate the results from other studies using 

the prediction equation, information is required on the test 

conditions: fuel RVP, tank temperature, and dispensed fuel 

temperature. Also the refueling losses need to be reported in 

total grams per gallon of refill, or in a form that can be 

readily converted to this form. Only a few of the previous 

studies met all of these criteria. 

In their tests involving Stage II vapor recovery vapor 

balance systems at a retail gasoline station, Scott 

Environmental arrived at estimates for uncontrolled 

emissions.[6] Their study involved two phases of testing: the 

first on thirty control vehicles at a service station and the 

second on random vehicles. For each phase, two series of 

vehicles were tested. Average RVP and dispensed temperature 

are only provided for the two series in the second phase of 

testing. These two series yielded baseline emissions of 5.505 

and 5.593 gm/gal. The average for the other factors are also 

given for these two series; RVP = 8.0286 and 8.6440, dispensed 

temperature = 81.265 and 81.0196 °F, and tank temperature =» 

81.867 and 82.0796 respectively. Using these conditions and 

the regression equation derived in this report, estimates of 

5.109 and 5.352 gm/gal are obtained. These are slightly lower 

than obtained by Scott, but still well within the range of 

uncertainty in the data.[6] 

In a study done by the Mobil Research and Development 

Corporation in 1978 a series of refueling emission tests were 

run on a 1978 Pontiac Sunbird. During these tests the vehicle 

was equipped with an onboard control system, so the total HC 

emissions given is the sum of the HC collected in the canister 

and the refueling emissions measured in the SHED. These tests 

were performed in a SHED, in the same general manner as the 

test in this study, with the only exception being that the 

vehicle was preconditioned by driving and not just heating of 

the fuel tank.[13] 

The Sunbird was tested at the following conditions: 

dispensed temperature = 82-85°F, AT = 0F°, and RVP ranging 

from 8.2 to I2.01bs. The resulting losses, along with the 

estimates from .this study are given below. The equation 

derived in this report is not strictly applicable at RVP levels 

under 9.0, but the estimates are given here regardless. Mean 

estimates from this study are generally on the high end of the 

ranges given by Mobil, but also note the variability in their 

test results. 
8.2-8.5 

8.6-9.0 

10.3-10.6 

11.2-11.4 

11.8-12.0 

8 

10 

3 

3 

3 

-36-

RVP tt Tests Total HC (gm/gal) This Study* 

3.72-6.82 5.52 

4.2-5.60 5.74 

5.9-7.1 6.54 

5.5-7.0 6.95 

7.0-7.2 7.24 

The Stanford Research Institute study involved tests on a 

26-gallon General Motors and a 26-gallon Ford fuel tank used in 

1973-4 vehicles, at a service station. The results from the 

tests on the GM tank at a fill rate of 5.3 gallons per minute 

and a fill of 20 gallons are given below along with this 

study's estimates at the given conditions.[9] These tests 

represent those most similar to this study's testing. Where 

the conditions fall within the ranges for which the EPA 

equation is applicable, the agreement is good, generally within 

.50 gm/gal. Only when the equation is extrapolated far beyond 

its applicable range is there a significant disagreement with 

the SRI results, illustrating the dangers of such extrapolation. 

GM/GAL 

RVP 

8.5 

8.5 

8.5 

8.5 

8.5 

8.5 

8.5 

8.5 

Exxon Research and Engineering performed a series of tests 

on 3 vehicles in 1978, in order to determine the efficiency of 

an onboard control system.[13] The vehicles tested were: a 

1978 Caprice, a 1978 Pinto, and a 1978 Chevette, and the test 

conditions were: AT = -1F°, T0 - 85° F, and RVP • 9.1 

psi. The resulting averages for each vehicle, along with 

predicted values from this study are given below. 

GM/GAL 

AT 

17 

0 rH 2 

27 

35 

41.5 

43 

To. 

79 

80 

80 

78 

76 

79 

79 

77 

SRI[2] 

5.13 

5.03 

4.82 

4.52 

3.07 

2.09 

1.26 

1.42 

This Study 

6.85 

5.28 

5.19 

4.92 

2.37 

1.88 

1.30 

0.94 

Difference 

1.72 

.25 

.37 

.40 

-.70 

-.21 

.04 

-.48 

Vehicle 

Caprice 

Pinto 

Chevette 

ERS.EC13] 

4 

4 

5 

9 

5 

4 

Th is 

6 

6 

6 

Study 

1 

1 

1 

Using 83.5°F and mid-range of RVP interval 
P.40 

-37-

^nt^an^es^ n tha, those tested here. 

F0ur prediction elation* that '—ur^^ T these 

AT have been found in the " l e TM M 1S o 25 associated with 

his a correlation coefficient, •:. of only here .[4] The 

£ ! sSo it has not ^exclude d 1^1 ^ \ e t cegion s whe re 

3 S l.

i

r?.^^'ir.fiv » below. 

r&PE9(EPA)[3] 

« rtnn*91(RVPHT0) - 0 .0012605(TT ) 

gm/gal - Wt-0-°*1703 o + o O ^ ^ 

R' - 0.945 . %E = c0

6to 90 °F TT - 50 to 90 -P 

R V P = 7 psi To - 50 to 90 o* T = ^ t Q 8 Q o p 

RVP = 10 PSI To = 40 to 80 oF T m 3 Q t Q 7(J o p 

RVP = 13 psi To - 30 no 

Exxon Rese^rcJwng^ncLi^^ 

R. . Q.951 SE = 12.4% 

RVP = 7 to 13 psi 

T o = 10 to 100 °F 

T T = 30 to 90 °F 

AT > -20 °F 

g^L&l78 + 0.1303<T.>^^ ^ 

R , = 0.5740 SE - 0.3873 gm/gal 

RVP = 8.8 to 9.0 psi 

T0 = 75 to 85 °F 

TT = 70 to 115 °F 

• A in thP CAPE-9, Exxon and Union 

The equations determined in thea CO T re.pectiy.ly. U . 

studies are based upon 140, 43 an ^ Exxo n studie s was 

2,3] The testing done in tne ^ 
P.41 

-38-

performed on a vehicle tank in a laboratory setting.[1,3] 

Union performed its testing on vehicles refueling at a retail 

gasoline station.[2] 

As is readily apparent, the form of these three equations 

differ among themselves, and from the equation derived in this 

study. This makes a direct comparison of the results somewhat 

difficult. Figure 27, however, shows plots of refueling losses 

versus for each equation and the Stanford results, at a 

dispensed temperature of 79°F and an RVP of 8.5 psi. An RVP of 

8.5 psi is slightly out of the applicable ranges for the Union 

results and those derived here, but the figure is still useful 

for comparison. Figure 28 shows a further comparison of this 

study's results to earlier work by EPA as cited in the Scott 

study.[6] This is shown in a separate figure as the conditions 

are slightly different from those show for the other studies. 

Figures 27 and 28 show very good general agreement between 

the results from the CAPE 9, Stanford, the earlier work by EPA, 

and this study, over their applicable ranges of AT. The 

studies by Union and Exxon yield somewhat lower estimates of 

refueling losses at negative values of AT, but their results 

are not radically different. All in all, considering the 

differences in testing apparatus and procedures, the results 

from the various studies tend to confirm each other and the 

results derived here. 

Considering the results from these studies, it appears 

that the prediction equation derived in this report generally 

provides reasonably accurate estimates of refueling emissions 

based upon the given parameters within its applicable parameter 

ranges. Therefore, there should be no problem in using it to 

determine average emission factors and to determine control 

system designs and efficiencies. 

IV. Calculation of Nationwide Emission Factors 

A. Introduction 

Analysis of the baseline test data has yielded an equation 

that can be used to calculate emission factors representative 

of various AT, T0, and RVP conditions within the 

approximate limits of the values for the original test 

parameters (see section III C 4). Given this ability to 

determine emission rates for different conditions, it then 

becomes necessary to determine the most representative 

conditions in order to calculate a refueling emission factor 

that will accurately reflect national uncontrolled in-use 

emissions levels. Because the conditions that determine 
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-40 -

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-41-

emission rates (basically temperature and volatility of the 

fuel) vary from region to region and from season to season 

within a given region, it will be necessary to identify 

regional and seasonal temperatures and fuel characteristics and 

then to apply the appropriate averaging to determine national 

emission factors. It is also important to examine seasonal 

emission factors to ensure that summer and winter emissions are 

not significantly different from the annual average value. 

There are two basic uses of a refueling emission factor: 

(1) to calculate air quality effects and (2) to determine 

health risk due to exposure to the pollutant in question. The 

air quality effect of VOC from refueling emissions consists of 

the role these emissions play in ozone formation. Ozone 

formation tends to be a seasonal phenomenon, with most NAAQS 

violations occurring during the spring and summer months, i.e, 

May through September. The emission factor used in air quality 

calculations should therefore appropriately reflect the 

conditions that are found during the ozone season. 

In addition to their role as ozone precursors, refueling 

emissions may also have environmental health effects. Benzene, 

a known human carcinogen, is present in small amounts in 

gasoline. In addition, recent studies have indicated that other 

species of VOC contained in refueling emissions are possible 

carcinogens.[15] Although the effect on humans is not fully 

known, refueling emissions may pose a health risk to service 

station employees, self-service gasoline customers, and persons 

residing near service stations. Because such exposure risk 

represents a year-round problem, the emission factor used in 

determining health risk should represent average annual 

conditions, although if there are significant seasonal 

variations the additional risk posed by these variations would 

have to be evaluated. 

The remainder of this report will begin with a discussion 

of the total emission factor, which includes both spillage and 

displacement losses. An appropriate spillage emission factor 

will be selected. The process for developing the displacement 

emission factor will then be described in detail, including the 

methodology used, sources of data, selection of- seasonal 

scenarios for air quality and environmental health effects, 

determination of representative temperature and fuel volatility 

parameters and emission factors for these scenarios. The 

question of seasonal differences in the emission factor will 

also be addressed. Finally, a representative national emission 

factor for refueling will be presented. 
P.45 

-42-

B. Description of Refueling Emission Factors 

There are two types of refueling losses that comprise a 

total refueling emission factor. These are spillage of liquid 

gasoline during the course of the refueling operation and 

displacement losses, or the vapor that is forced out the 

fillpipe during refueling. Displacement losses occur during 

every refueling operation, while spillage or "spitback" is a 

more infrequent occurrence. 

1. Spillage Losses 

A varying portion of the total refueling loss results from 

the spillage of liquid gasoline during the refueling process. 

The amount of such spillage can vary from a few drops on the 

side of the car or pavement as the fueling nozzle is withdrawn 

from the fillpipe to a cup or more spurting out on the ground 

as a result of "spitback" due to poor fillneck design or a 

malfunctioning fuel nozzle. Probably the majority of spills 

are less extreme, coming about as a result of motorists or 

service station attendants attempting to "top off" the vehicle 

tank by restarting the nozzle after automatic shutoff has 

occurred. Such spills are normally not large, on the order of 

a tablespoon or so. A spill of one tablespoon leaves a 9 to 10 

inch diameter circular spot on the service station pavement and 

results in emissions of about 10 grams. Thus on a 10 gallon 

fill, the spillage would equal about one gram per gallon of 

fuel dispensed. Larger spills such as those accompanying 

spitbacks or nozzle malfunctions can lead to significantly 

higher emissions. A one-half cup spill for the same 10 gallon 

fill leads to emissions of about 8 grams per gallon. Thus, 

overall, spills are of concern. 

Of course not every fillup, or even every attempt at 

"topping off" results in a fuel spill and different amounts of 

fuel are spilled each time. Unfortunately very few data are 

available regarding either the quantity or the estimated 

frequency of fuel spills, and there is considerable variance in 

the existing estimates. EPA's emission factor document (AP-42) 

presents a value of about 0.30 grams per gallon based on a 

comprehensive study conducted by Scott Research Laboratories in 

the early I970's.[l6] However, an in-depth review of this 

study reveals the authors belief that the- spillage rate 

estimates should be viewed as minimum values, rather than 

averages, due to the presence of observers, the technique used 

to estimate spill amounts, and the fact that the stations 

studied were primarily full serve rather than self serve.[17] 

However, another EPA contractor report cited an estimate of 

1.36 grams per gallon, and a 1980 Calfornia study conducted by 
-43-

the South . Coast Air Quality Management District provided 

information which indicated an average spillage rate of about 

0.80 grams per gallon for uncontrolled nozzles.[18,19]. it 

should be noted that the latter study included the brief period 

of fuel shortages in 1979, which may have encouraged an 

abnormal amount of "topping off" of fuel tanks and hence 

slightly higher than normal spillage. The wide variation in 

the available data on spillage rates (more than a factor of 

four among the three studies) is of some concern. While there 

appears to be good reason for the variation, the data is 

inadequate to allow determination of a revised emission 

factor. In the absence of more definitive information on this 

topic, the .30 grams/gallon rate contained in AP-42 seems to 

represent the best available estimate of the spillage emission 

factor, so this value will be used in this analysis. The 

remainder of the discussion will focus on the displacement 

emission factor, but it should be noted that the emission 

factor for spillage must be added to the displacement emission 

factor in order to arrive at a total refueling emission factor. 

2. Displacement Losses 

As discussed earlier, there are three primary factors and 

several secondary factors that determine the displacement 

emission rate for refueling operations. The primary factors 

are (1) the dispensed temperature (TD) of the gasoline (2) 

the Reid Vapor Pressure (RVP) of the gasoline and (3) AT, or 

the difference between the temperature of the residual gasoline 

in the vehicle tank (TT) and the dispensed temperature of the 

gasoline used to refill the tank (ie. TT -TD ). To develop 

emission factors for refueling operations, it will be necessary 

to look at these parameters on a seasonal and national basis. 

The most significant of the secondary factors are fuel tank 

configuration differences, the effects of which have been 

described in sections II and III above, and differences between 

the RVP of the dispensed fuel and the residual fuel in the 

tank, due to weathering of the tank fuel. 

C. Calculation of Displacement Emission Factors 

This section will derive nationwide average values for the 

three major determinants, AT, T0, and RVP, from which the 

uncontrolled displacement emission factors for several 

scenarios will then be calculated. 

1. Methodology 

Overall, the methodology used in this process is to weight 

the available regional temperature and RVP data by regional 

highway fuel consumption to determine average national values 
-44-

for the appropriate time periods for each scenario to be 

evaluated. These average values can then be used with the 

multiple linear regression equation developed earlier to 

calculate representative emission factors. The available data 

indicate that there is a considerable amount of regional and 

seasonal variation in the the temperature and RVP parameters, 

making such a weighting process necessary. Also, the fuel 

consumption pattern is far from uniform throughout the U. S. 

and the available data are not all aggregated at the same 

levels. Fuel consumption and RVP data are available on a 

monthly state-by-state basis while AT and T0 data are 

available only on a monthly regional basis. The methodology 

used to aggregate and weight these parameters will be discussed 

following a brief description of the sources of the fuel 

temperature, RVP and fuel consumption data that were used. 

2. Sources of Data 

a. 

Fuel Temperature 

Dispensed temperature and AT data used for calculating 

emission factors are available from a 1975 gasoline temperature 

survey conducted for the American Petroleum Institute (API) by 

the Radian Corporation. [20] The year 1975 is considered to be 

a representative year in terms of temperature, since the 

average annual ambient temperature was within one degree of the 

30 year mean. The study surveyed 56 U.S. gasoline stations 

located in 22 cities; these were grouped into six geographic 

regions. The six regions and the locations for the stations 

surveyed are shown in Figure 29, and the monthly AT and T0 

values from the survey are shown in Appendix B. 

Not all of the stations reported data for all months of 

the year, resulting in a few gaps in the data. The most 

serious of these gaps occurred in the Pacific Northwest (region 

6 in Figure 29) where AT data were reported only for the 

month of May. Since the Pacific Northwest accounts for only 

about 3.5 percent of the gasoline consumed for highway use in 

the U.S., it was concluded that this region could be omitted 

from the analysis without seriously affecting the accuracy of 

the results. Alaska and Hawaii were also omitted from the 

study, since no AT or T0 data were available from these 

states. Other minor gaps of a month or so in AT and T0 

data, primarily in the North Central U.S. and the Far West 

(regions 4 & 5), were filled by points interpolated from the 

existing data. 
P.48 

-45-
\ 

P.49 

-46-

b. Nationwide Fuel Consumption 

Nationwide fuel consumption (gasoline) by state was taken 

from the 1983 version of the DOT/FHwA publication entitled 

Highway Statistics - Table MF-26. This table contains 

estimates of monthly gasoline consumption for each state and 

the District of Columbia. Table MF-26 is shown in Appendix B. 

To allow for further calculations, the monthly state fuel 

consumption figures were summed for each region thus providing 

monthly regional fuel consumption values. 

c. RVP 

The RVP data were taken from 1983 ASTM maximum 

specifications for the U.S.[21] The maximum specifications 

were used rather than current actual levels on the assumption 

that recent increases in RVP would continue and that by 1989 

in-use RVP levels would be essentially at the maximum values 

specified by. ASTM. This is already the case in some areas of 

the country. The RVP values for each state and month are also 

shown in Appendix B. 

To get the RVP data on the same level of aggregation as 

the temperature data, the state RVP data was divided into the 

same regions as the temperature data and then consumption 

weighted to get weighted RVP for each region in each month. 

3. Air Quality and Health Effects Scenarios 

To facilitate assessment of seasonal variation in the 

emission rates, five seasonal air quality and health effects 

scenarios were established and AT, TD, and RVP values were 

calculated for each. The first scenario is simply the annual 

average value for the nation or region. Two additional 

six-month scenarios were chosen to represent warm weather 

versus cold weather conditions. "Winter" is comprised of the 

months October through March, while "Summer" consists of the 

months April through September. Two additional scenarios were 

chosen to represent the months in which most ozone violations 

occur. These include a "Five Month" scenario (May through 

September), and a "Two Month" scenario for the two peak ozone 

violation months (July and August). 

4. Consumption Weighting Calculation 

In order to calculate national average AT, T0 , and RVP 

values for the five scenarios mentioned above, monthly regional 
-47-

data were consumption-weighted by the regional fuel consumption 

values for' the months in question. As explained earlier, 

monthly state RVP and fuel consumption values were aggregated 

on the same monthly regional basis as the T0 and AT data. 

The generalized equation for calculating consumption weighted 

values for each scenario is as follows: 

n 

I (ATR.rl)(FCR,„) 

AT= R.M-I 

FC Tota l 

Where R = region number from Figure 29 

M = month number (of the seasonal scenario, not 

necessarily of the calendar year) 

n = number of months and number of regions evaluated in 

a given scenario 

ATR,n = temperature differential (AT) for region R 

during month M 

F CR ,M = fuel consumption for region R during month M 

FCrot.i = total national fuel consumption (less region 

6, Alaska and Hawaii). 

The key parameter shown in the equation above is AT. The 

consumption weighted values for the other two key parameters 

for any given scenario can be determined by substituting the 

appropriate monthly T0 and RVP values in the equation above. 

This can be done for each of the scenarios mentioned above to 

get the appropriate values of the key parameters for use in the 

refueling emission equation. 

The results of these weighting calculations are shown in 

Table 6. Regional and national average AT, T0 and RVP 

information is presented for five scenarios: annual average, 

summer, winter, five month ozone season and two month peak 

ozone season. Regional fuel consumption values used in the the 

weighting calculations and percentages of total fuel 

consumption for each region are also shown for comparison 

purposes. As explained above, Region 6 (Pacific Northwest) has 

been omitted, as have Alaska and Hawaii. As would be expected, 

TD, RVP and AT values vary both seasonally and from region 

to region for any given season. Reasons for this variability 

are discussed below. 

As can be seen from the table, dispensed fuel temperatures 

vary seasonally and from region to region. This is due largely 

to climatic factors such as ambient temperature and" the amount 

of solar radiation. Other relevant variables include the 

volume and depth of the underground service station tanks, 

layout of the fuel piping, composition of the surface over the 

tanks and associated piping (e.g. concrete, asphalt, grass) and 
P.51 

' 

SCENARIO: ! 

avpraae Annual 

Fuel Consumpt. 

(gal x IO6) 

% Tota l 

RVP (PSI) 

A T (°F) 

TD (°F) 

Summer (Apr-Oct) 

Fuel Consumpt. 

(gal x IO6) 

% Tota l 

RVP (PSI) 

A T (°F) 

TD (°F) 

Winter (Oct-Mar) 

Fuel Consumpt. 

(gal x IO6) 

% Tota l 

WP (PSI) 

A T (°F) 

TD (°F) 

Weighted 

Siat'l Avg. 

96,050.4 

100.0 

12.6 

+4.4 

68.9 

51,846.3 

100.0 

11.5 

+8.8 

76.2 

44,204.4 

100.0 

13.9 

-0. 8 

60.3 

-48 -

Table 6 

r-mr-H^ P and RVP Parameters 

REGION: 

1 2 

N.T^st S.East 

3 

S.West 

41,658.5 20,381.2 11,977.6 

43.4 21.2 

13.3 12.4 

+5.7 +4.0 

62.3 81.8 

22,815.1 10,689.0 

44.0 20.6 

12.2 U. 4 

+10.7 +6.8 

70.7 86.7 

18,843.5 9,692.1 

42.6 21.9 

14.6 13.4 

-0. 3 +0.9 

52.0 76.4 

12.5 

11.4 

+3.7 

70.5 

6,232.4 

12.0 

10.1 

+7.6 

78.6 

5,745.3 

13.0 

12.8 

-0. 4 

61.8 

4 

N.Cent. 

; 

5 

Far W. 

10,225.6 11,807.6 

10.6 

12.6 

+5.5 

66.2 

5,690.2 

11.0 

11.2 

+11.7 

74.3 

4,535.5 

10.3 

14.3 

-2. 4 

56;1 

12.3 

11.7 

+0.1 

70.5 

6,419.7 

12.4 

10.5 

+3.9 

77.2 

5,388.0 

12.2 

13.3 

-4. 4 

62.4 
-49 -

2 3 4 5 

1

 „«*.,.•. <? u»«f N.Cent. FarW. 

Scenario 

Nfest S.East S.West 

Nat V AV9JL_

 N - ' a s

-

Ozone- 5 to._(Ma£geptl 

n ne^: n ^ 944 4 4,869.o D,**oo.^ 

A , QQ 5 8 19,459.4 8,956.0 5,244.4 

Fuel Consumpt. 43,995.a (gal x IO6) 

% Total 

RVP (PSD 

A T CF) 

TDCF) 

100.0 

11.3 

+9.4 

78.8 

44.2 

12.0 

+11.5 

73.8 

20.4 

11.2 

+7.5 

88.0 

11.9 

9.9 

+7.1 

80.8 

11.1 

10.9 

+12.1 

79.0 

12.4 

10.3 

+5.1 

79.0 

Z ^664. 7 8.326.2 3,760.0 2.147.7 2,103.0 2.327.8 

Fuel Consumpt. IB,M». ' 

(gal x IO6) 

% Total 

RVP (PSI) 

A T CF) 

TD CF) 

100.0 

10.9 

+9.9 

82.7 

44.6 

11.5 

+12.5 

78.0 

20.1 

10.9 

+8.2 

90.5 

11.5 

9.8 

+7.0 

83.5 

11.3 

10.5 

+13.3 

86.5 

12.5 

10.0 

+3.2 

83.0 
-50-

protection .from solar radiation for the tank system. Although 

there is a strong correlation between ambient temperature 

(TA) and dispensed temperature, variation exists due to these 

other factors. In general, the Radian study for API shows the 

average dispensed temperature parallels the average ambient 

temperature curve, with a positive offset (i.e., TD is always 

higher than TA ). The amount of the offset varies seasonally 

and regionally, undoubtedly due to climatic differences. 

The RVP values shown in the table are ASTM maximum 

recommended values. Figure 30 shows the average seasonal and 

regional variation in these ASTM RVP values and the resulting 

national averages for winter and summer. The regions by which 

these data are aggregated are those shown in Figure 29. ASTM 

assigns each state a "volatility class" and specifies maximum 

recommended monthly RVP limits based on the climatic and 

topographic factors. The five volatility classes are 

designated A, B, C, D, and E, corresponding to maximum RVP 

limits of 9, 10, 11.5, 13.5, and 15 psi, respectively. In 

addition, a number of states have formally adopted RVP limits 

similar to the ASTM recommended levels.[22] Particularly 

noteworthy is California, where RVP is limited to 9 psi during 

the months of the highest ozone concentrations in order to 

decrease VOC emissions. 

In-use RVP is essentially determined by the gasoline 

refiners, subject to state laws and voluntary compliance with 

the ASTM recommended limits. RVP varies seasonally as well as 

regionally, based primarily on how the climate and topography 

of an area affect vehicle operation. For example, RVP is 

higher in the winter to assist in cold starting but decreases 

in summer to avoid vehicle driveability problems such as vapor 

lock. RVP values are generally higher for the northeastern 

U.S. than the southeastern U.S. In general, for any given 

season or area, RVP is higher as ambient temperature for any 

given month decreases. The overall trend in in-use RVP has 

been toward higher and higher values in recent years, due to 

changes in vehicle design and gasoline refining practices, 

leading to the conclusion that by 1990 the in-use values will 

approximate the ASTM maximum limits. 

The final factor, AT, also varies seasonally, with 

positive values being more predominant in the summer and 

negative values more prevalent in winter. Although there is a 

certain amount of regional variation, the seasonal values are 

very similar for all areas of the country. 

There is also a certain amount of diurnal variation that 

affects AT values, which explains the presence of some 
V) 

0-

I 

CL 

SEASONAL RVP VALUES 

AVG ANN 

EZl R1 [S3

 R2 

NAT. AVG. 

SUMMER 

SEASONAL SCENARIOS 

Figure 3 0 

WINTER 

isa

 R5 

I 
P.55 

-52-

negative values in the summer and positive values in the 

winter. - T0 is more stable than TT due to the insulating 

effect of the ground in which the service station storage tanks 

are buried. Since vehicle tank temperatures follow ambient 

temperatures more closely, the likelihood is strong that TT 

will be lower for those vehicles fueled in the morning, 

resulting in negative, or at least less positive, AT 

values. Conversely, diurnal heating would likely result in 

higher TT values in the afternoon, resulting in positive 

ATs. The distance a car is driven before refueling also 

affects TT (TT increases with distance driven, up to a 

point) which in turn affects AT. Since these diurnal 

effects are recurring and ongoing, one would expect the 

differences between summer and winter ATs to be caused by 

climatic and not diurnal variations. 

5. Emission Rates 

Given the weighted regional and national average T0, 

AT and RVP values in Table 6 for each of the five scenarios 

under consideration, we are now prepared to calculate the 

emission rates for each of the scenarios and to assess how the 

variation in the key parameters affects emission rates. These 

emission rates for the different scenarios are calculated quite 

simply by substituting the T0, AT and RVP values of Table 6 

into the multiple linear regression relationship developed 

earlier (given below) and solving for the emission rate (ER). 

ER = -5.909 - 0.0949AT + 0.0884 T0 + 0.485 RVP 

The results of these calculations for each of the five 

scenarios are shown in Table 7. This emission rate data can be 

compared regionally within each scenario and between the 

various scenarios on a seasonal basis for each region and 

nationally. 

Turning first to the regional evaluation within each 

scenario, several points should be noted. First, overall, the 

regional values for each scenario are relatively uniform given 

the variation seen in the key parameters of Table 6. All 

values fall within + 10 percent of the national average for 

that scenario, with the exception of the southeastern U.S 

(Region 2). In each of the five scenarios the emission rate 

expected in the Southeast exceeds the national average for that 

scenario by between 16 and 19 percent. . The higher emission 

rates in the southeastern US apparently occur because of the 10 

to 16F° higher dispensed temperatures encountered there, as 

compared to the national average. Simply by using the 

coefficient for T0 in the emission rate equation, it can be 
-53-

Table 7 

Displacement Emission Factors 1/ 

P.56 

REGION: 

SCENARIO: Nat'l Avg. 

Average Annual 5.9 

Summer (Apr-Sep) 5.6 

Winter (Oct-Mar) 6.2 

Ozone-5 mo. (May-Sep) 5.6 

02one-2 mo. (Jul-Aug) 5.7 

1 

N.East 

5.5 

5.2 

5.8 

5.3 

5.4 

S 

2 

East 

7.0 

6.6 

7.2 

6.6 

6.6 

S 

3 

West 

5.5 

5.2 

5.8 

5.4 

5.6 

N 

4 

Cent. 

5.5 

5.0 

6.2 

5.2 

5.6 

5 

Far W. 

6.0 

5.6 

6.5 

5.6 

6.0 

T7~ Displacement losses only - a spillage factor must be added to derive a total 

refueling emission factor. 
-54-

determined that the 10 to 16F° difference in T0 results in an 

increase- of 0.9 to 1.4 g/gal in the emission for the various 

scenarios. This easily accounts for the significantly higher 

emission rate in the this region. 

Climatological differences offer the most likely 

explanation for the higher dispensed temperatures in the 

Southeast. As explained earlier, the average T0 value 

generally follows the trend of the annual average ambient 

temperature curve for any given region, but there is always a 

positive offset (i.e., the T0 value is greater than the 

average ambient temperature), probably because of solar heat 

gain and the thermal storage effect of the ground, which in 

turn are modified by the other factors noted above in section 

C-4. The magnitude of the offset varies during the course of 

the year for most regions, particularly where the ground may be 

frozen during the winter months. In such areas T0 may 

approach the ambient temperature in the Spring, when the 

ambient temperature rises relatively quickly while the soil 

temperature increases more gradually. The offset for the 

Southeast, on the other hand, is relatively constant throughout 

the year, likely because over most of the area the ground never 

freezes and because of greater solar gains and higher ambient 

temperatures, particularly during the Winter months. 

Second, comparing the seasonal (summer and winter) 

emission rates to the average annual rates for each region, all 

the emission rates are within +10 percent of the average annual 

value except for the North Central U.S. In this case the 

seasonal variation is on the order of 12-13 percent, due to 

slightly greater seasonal variation in the absolute values of 

the key parameters. This relatively small seasonal variation 

in the emission factors is likely due to the existence of 

offsetting factors in the conditions that determine both Winter 

and Summer emission rates. In the Winter months, RVP's are 

high and AT values tend to be more negative than during the 

Summer. Both of these trends would tend to increase emissions, 

but they are offset by lower dispensed temperatures, which tend 

to decrease emissions. Conversely, during the Summer dispensed 

temperatures are higher, which would increase emissions, but 

the higher temperatures are offset by lower RVP's and positive 

AT values, both of which tend to decrease emissions. 

Third, comparing the. two ozone scenarios to the average 

annual scenario, the emission rates for all five regions and 

the national average do not vary by more than 10 percent. In 

this case the average annual values for each region exceed the 

ozone scenario values in a range of 0 to about 6 percent. So 

overall there is good agreement between the average annual 
P.5B 

-55-

emission rates 

prone months. This 

level. 

and the emission rates expected in the ozone 

is true for all regions and on a national 

6. Effects of Fuel Weathering 

In addition to the three primary factors discussed above, 

fuel weathering also affects refueling emission rates. Fuel 

tank weathering results in a difference in RVP between the 

dispensed fuel and the residual fuel in the vehicle tank, with 

fuel in the tank losing volatility due to the evaporation of 

lighter ends in the gasoline. The very limited amount of 

baseline testing that was done with lower RVP fuel in the 

vehicle tank indicates that an increase in emissions, on the 

order of a gram per gallon, resulted from an RVP difference of 

approximately 1.9 psi between the tank and the dispensed fuel 

(see Section III.C). This general phenomenon was also 

observed in the SRI study.[2] Unfortunately, neither the EPA 

nor the SRI data are adequate to fully characterize the effect 

of the RVP difference, although they do show the direction and 

give a rough idea of the magnitude of the change. 

In order to be able to include the effect of tank fuel 

weathering in the emission rate calculation, one would also 

need to know the average amount of in-use weathering that 

the effect of the 

refueling emission 

vehicle and fuel 

can be determined 

of tank weathering 

occurs between refuelings, in addition to 

resultant difference in RVP values on the 

rate. This includes both the different 

effects. Since neither of these variables 

with any certainty at this time, the effect 

has not been included in the emission factor calculation. 

Although refueling emissions may thus be somewhat understated, 

this effect may be partially offset by the method of RVP 

determination for the calculation. Use of the ASTM maximum RVP 

limits represents EPA's best judgment of future RVP levels. 

However, if in-use RVP levels should be lower than these 

maximum values, the resulting decrease in the emission factor 

would tend to be at least partially offset by an increase in 

refueling emissions due to fuel weathering. 

D. Conclusions 

At the beginning of this investigation it was felt that it 

might be necessary to develop both a seasonal emission factor 

for air quality calculations and an average annual emission 

factor for health exposure risk calculations. However, the 

relative uniformity of the seasonal emission factors indicates 

that the average annual values can be used for both purposes 

without introducing any significant error into the air quality 
-56-

calculations. If only air quality calculations were involved, 

it might be more appropriate to use only a summer emission 

factor, although by so doing two important "by-products" of the 

air quality calculation, the emissions inventory calculation 

and the calculated lifetime emissions reduction per vehicle, 

would both be understated. An annual average would be more 

appropriate for these latter two purposes as well as for health 

exposure risk calculations. 

On the other hand, use of an average annual emission rate 

for air quality determinations may theoretically overstate the 

air quality benefits somewhat. The difference between the 

summer and average annual emission factors is relatively small 

(less than 5 percent), however, and any differences in air 

quality calculations, i.e. SMSAs brought into compliance or 

percent change in air quality, would likely disappear in the 

roundoff of the EKMA model. Thus in practical terms, it would 

likely be very difficult to see any differences in the air 

quality outputs resulting from the use of the average annual 

values, whereas there are. real advantages to its use in terms 

of emissions inventory, lifetime emissions and costeffectiveness calculations. 

Finally, it does not appear that there will be a need for 

seasonal emission factors for health effects purpose as a 

result of changes in the amount of benzene and other 

potentially hazardous species in the total VOC emitted. Such 

emissions are a function of the percentage of the hazardous 

pollutant present in liquid gasoline and the same temperature 

considerations that affect the basic VOC emission rate. In 

order to have significant seasonal variation in the emissions 

of these hazardous species, then, either the seasonal 

percentage of these species in the liquid gasoline would have 

to vary significantly or, since such emissions are normally 

expressed as a percentage of total VOC emissions, winter and 

summer VOC emission factors would have to differ significantly 

from the annual average. As stated above, the latter condition 

Correspondingly, the 1983/84 NIPER gasoline 

significant difference between tha winter and 

percentages in liquid gasoline. For these 

summer and winter benzene fractions in the 

averaged about 1.3 percent.[23,24] Similar 

available for other potentially hazardous species, 

no reason to believe that the liquid fraction of 

is not the case 

surveys show no 

summer benzene 

surveys average 

liquid gasoline 

data are not 

but there is 

these species varies regionally or seasonally. Therefore it is 

reasonable to conclude that seasonal differences in the 

emission factors will not necessitate separate emission factors 

for either health effects or air quality purposes. 
P.60 

-57-

c it was decided to use the average 

For these reasons, it "a s

 s pe r gallon for all 

per gallon. 
P.61 

Appendix A 

BASELINE TEST RESULTS 
P.62 

Supreme 

l983 OLdsncoile Cutlass 

Oisp^el T^ratute - 82'F 3 K*s 

Test 

845638 

845639 

845637 

845632 

845636 

845631 

845628 

845630 

850113 

850114 

850115 

850117 

851354 

851355 

845950 

845951 

845945 

845947 

850057 

850104 

845943 

845944 

845946 

850105 

850106 

845941 

845942 

845948 

845642 

845641 

845627 

845294 

845625 

RVP 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

12.6 

12.6 

12.6 

12.6 

12.6 

TCF) 

1.5 

0. 

10.8 

8.1 

22.0 

18.5 

36.7 

37.0 

12.0 

7.7 

12.3 

11.9 

2.3 

1.5 

-1.1 

-.8 

11.0 

10.0 

10.0 

11.1 

17.0 

21.7 

20.5 

17.2 

18.0 

34.0 

39.5 

38.8 

-2.0 

7.5 

8.2 

16.6 

19.0 

Disp. 

TempCF) 

80.5 

82.0 

82.0 

83.9 

81.0 

83.5 

82.3 

82.0 

80.5 

83.3 

80.0 

79.8 

81.7 

81.5 

81.0 

83.0 

81.0 

83.2 

82.0 

80.8 

85.0 

80.8 

83.0 

83.8 

81.8 

86.0 

82.0 

81.2 

Losses 

(gm/gal) 

5.209 

5.456 

5.021 

5.308 

4.407 

4.632 

3.115 

2.918 

4.934 

4.934 

4.331 

5.126 

5.060 

5.133 

7.831 

8.074 

6.490 

6.133 

6.395 

5.947 

4.842 

4.432 

5.743 

5.327 

5.007 

3.830 

3.500 

3.514 

845289 

845290 

845280 

845292 

850110 

850111 

850112 

851356 

851357 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

-11.0 

8.3 

29.0 

27.8 

1.5 

1.5 

2.2 

15.2 

8.4 

82.5 

84.0 

84.0 

84.0 

81.0' 

8.938 

7.366 

6.892 

6.290 

6.081 

Lig. 

TempCF) 

82.0 

82.0 

92.8 

92.0 

103.0 

102.0 

119.0 

119.0 

92.5 

91.0 

92.3 

91.7 

84.0 

83.0 

79.9 

82.2 

92.0 

93.2 

92.0 

91.9 

102.0 

102.5 

103.5 

101.0 

99.8 

120.0 

121.5 

120.0 

80.5 

91.5 

92.2 

100.6 

100.0 

Disp. Heat 

Vap. Disp. Losses Time Time 

TempCF) Gals (gms) (nm.) (mm.) 

Dispensed Temperature 

91.0 

92.0 

91.0 

91.2 

90.5 

90.5 

90.0 

88.0 

92.0 

6.952 

6.324 

4.257 

4.097 

6.470 

6.831 

5.887 

4.700 

6.060 

83.0 

83.0 

93.9 

92.5 

102.0 

100.5 

116.0 

117.0 

92.3 

93.0 

93.4 

90.5 

82.5 

82.5 

82.5 

83.0 

92.3 

92.5 

93.0 

93.0 

102.0 

102.0 

103.0 

102.5 

98.5 

118.3 

118.0 

113.5 

83.0 

92.5 

92.5 

102.0 

101.0 

80.0 

100.3 

120.0 

119.0 

92.0 

92.0 

92.2 

103.2 

100.4 

14.8 

14.7 

14.6 

14.6 

15.0 

15.5 

14.8 

14.6 

15.1 

15.1 

15.1 

15.1 

15.0 

15.0 

14.8 

14.8 

14.7 

15.0 

15.2 

15.0 

14.6 

14.8 

14.8 

15.0 

14.9 

15.3 

14.6 

14.8 

14.5 

14.5 

14.8 

14.5 

14.9 

77.1 

80.2 

73.3 

77.5 

66.1 

71.8 

46.1 

42.6 

74.5 

74.5 

65.4 

77.4 

75.9 

77.0 

115.9 

119.5 

95.4 

92.0 

97.2 

89.2 

70.7 

65.6 

85.0 

79.9 

74.6 

58.6 

51.1 

52.0 

129.6 

106.8 

102.0 

91.2 

90.6 

2.52 

2.53 

2.58 

2.67 

2.63 

2.70 

3.00 

2.58 

1.97 

1.98 

1.98 

2.02 

1.98 

1.97 

3.30 

3.42 

3.25 

3.33 

1.98 

2.00 

3.35 

3.13 

3.33 

2.05 

1.97 

3.50 

3.27 

3.23 

28.00 

24.00 

52.00 

50.00 

36.00 

37.00 

74.00 

67.00 

42.00 

32.00 

30.00 

48.00 . 

28.00 

32.00 

24.00 

24.00 

60.00 

46.00 

46.00 

45.00 

35.00 

40.00 

37.00 

39.00 

39.00 

68.00 

61.00 

72.00 

= 92°F 3 HVPs 

81.8 14.5 100.8 

101.0 14.2 89.8 

119.0 14.3 63.0 

116.0 14.5 59.4 

92.5 14.9 96.4 

93.5 15.4 105.2 

94.2 15.1 38.9 

100.0 15.0 70.5 

97.0 15.1 91.5 

3.62 

3.58 

3.83 

3.68 

3.38 

2.88 

2.95 

2.78 

2.82 

2.05 

2.07 

2.00 

2.00 

2.05 

25.00 

43.00 

60.00 

39.00 

41.00 

26.00 

38.00 

67.00 

67.00 

34.00 

34.00 

36.00 

44.00 

32.00 
P.63 

845931 

845932 

845935 

845937 

850054 

850053 

845938 

845939 

845933 

845936 

850055 

850056 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

845956 10.0 

845957 10.0 

845954 10.0 

845955 10.0 

845953 10.0 

-10.5 

-10.3 

2.Q 

1.0 

2.5 

-1.0 

9.5 

10.1 

22.1 

30.6 

25.9 

28.8 

-11.0 

-10.0 

1.8 

2.0 

11.8 

845107 

845276 

845102 

845103 

845109 

845105 

845106 

845275 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

-10.8 

-11.0 

2.0 

-1.0 

-3.2 

7.1 

3.0 

27.5 

92.0 

91.3 

90.0 

91.0 

90.5 

93.0 

92.0 

91.8 

92.0 

90.9 

93.0 

91.2 

91.0 

90.0 

90.2 

90.0 

90.8 

845286 

845287 

345961 

845959 

850904 

850913 

9.0 

9.0 

10.0 

10.0 

11.9 

11.9 

10.5 

-3.5 

-6.0 

-3.9 

10.250 

11.431 

8.307 

7.270 

10.060 

9.765 

8.066 

7.815 

4.921 

3.311 

4.066 

4.821 

8.597 

8.128 

6.966 

7.240 

6.479 

81.5 

81.0 

92.0 

92.0 

93.0 

92.0 

101.5 

101.9 

114.1 

121.5 

118.9 

120.0 

80.0 

80.0 

92.0 

92.0 

102.6 

81.5 

83.0 

91.5 

93.0 

90.8 

92.0 

102.5 

103.0 

109.9 

119.0 

117.8 

117.2 

82.3 

83.0 

93.0 

92.3 

102.0 

Single Blanket Data 

90.8 

90.0 

90.0 

92.7 

93.2 

91.6 

91.5 

92.5 

92.5 

92.0 

6.353 

6.651 

5.980 

6.153 

6.554 

5.027 

5.060 

3.453 

80.0 

79.0 

92.0 

91.7 

90.0 

98.7 

99.5 

120.0 

Etoad Prep Data 

15.2 

15.3 

15.0 

15.2 

14.9 

15.3 

15.2 

15.1 

15.1 

14.8 

15.2 

15.1 

14.9 

14.9 

14.8 

15.0 

14.6 

92.0 

91.6 

4.815 

6.060 

7.985 

6.514 

Dispensed Fuel RVP 

850885 11-9 

850887 11.9 

850901 H -9 

850902 11-9 

0.0 

3.1 

3.2 

3.0 

4.7 

4.0 

92.0 

90.3 

9.566 

8.731 

103.0 

88.5 

86.0 

37.7 

. 11.9 

92.0 

93.9 

78.0 

76.0 

86.5 

86.0 

84.0 

95.6 

96.4 

114.0 

105.9 

90.0 

87.5 

88.7 

155.8 

174.9 

124.6 

110.5 

149.9 

149.4 

122.6 

118.0 

74.3 

49.0 

61.8 

72.8 

128.1 

121.1 

103.1 

108.6 

94.6 

4.52 

4.53 

3.98 

3.77 

3.08 

3.28 

4.22 

4.22 

4.05 

3.60 

2.55 

2.32 

3.48 

3.43 

3.33 

3.42 

3.33 

32.00 

24.00 

46.00 

53.00 

40.00 

42.00 

40.00 

39.00 

67.00 

65.00 

49.00 

58.00 

21.00 

24.00 

48.00 

48.00 

35.00 

15.0 

14.6 

15.0 

15.0 

14.8 

15.0 

14.9 

15.0 

14.6 

13.4 

95.3 

97.1 

89.7 

92.3 

97.0 

75.4 

75.4 

51.8 

2.85 

2.83 

2.93 

2.97 

2.93 

2.93 

2.80 

2.87 

36.00 

42.00 

96.00 

178.00 

74.00 

212.00 

173.00 

306.00 

13.5 

14.2 

70.3 

81.2 

107.8 

92.5 

2.60 

3.15 

3.22 

132.00 

172.00 

185.00 

159.00 

TanK Fuel RVP = 10.0 

88.0 

90.3 

14.5 

14.5 

^ e Vapor-Li^id Textur e Differences 

90.8 

91.0 

89.0 

89.0 

8.220 

8.140 

8.947 

9.093 

94.0 

94.0 

93.7 

93.0 

86.8 

87.0 

104.0 

102.5 

15.0 

15.0 

15.0 

15.0 

138.7 

126.6. 

123.3 

122.1 

134.2 

136.4 

2.27 

2.25 

2.07 

2.10 

2.10 

2.07 

16.00 

19.00 

16.00 

16.00 

36.00 

34.00 
P.64 

!984 Ford Escort 

851161 

851162 

851163 

851165 

851164 

851166 

851213 

851214 

850304 

850012 

850014 

850311 

850314 

850312 

850313 

850013 

850303 

850011 

850310 

850309 

850307 

850308 

851160 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

9.0 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

3.7 

4.0 

9.3 

12.5 

21.2 

22.5 

10.5 

20.5 

1.5 

12.0 

12.7 

2.7 

11.8 

11.1 

13.4 

3.7 

3.7 

13.3 

4.5 

12.0 

22.0 

23.0 

20.2 

851167 9.0 

851168 9.0 

851169 9.0 

851211 9.0 

846446 

846447 

350305 

850306 

11.9 

11.9 

11.9 

11.9 

Dispensed Temperature 

80.0 

79.0 

80.7 

81.0 

80.3 

78.5 

81.0 

80.5 

81.2 

80.0 

80.3 

80.0 

81.2 

81.0 

79.1 

80.0 

80.0 

79.6 

78.5 

80.5 

80.5 

80.0 

80.0 

8.9 

4.5 

4.8 

6.0 

2.0 

.7 

7.5 

5.0 

4.456 

4.308 

4.269 

4.574 

4.221 

3.159 

4.673 

4.346 

6.091 

5.750 

5.606 

5.595 

5.694 

5.654 

5.455 

6.255 

5.991 

5.890 

6.279 

6.077 

5.390 

5.202 

5.567 

83.7 

83.0 

90.0 

93.5 

101.5 

101.0 

91.5 

101.0 

= 80"F 2 RVPs 

83.0 10.3 

83.0 10.4 

91.9 10.4 

92.5 10.8 

101.8 10.4 

102.5 10.7 

91.7 10.4 

101.0 10.4 

82.7 

92.0 

93.0 

82.7 

93.0 

92.1 

92.5 

83.7 

83.7 

92.9 

83.0 

92.5 

102.5 

103.0 

100.2 

Dispensed Temperature = 

85.0 

89.5 

89.7 

89.0 

92.5 

92.3 

4.740 

5.221 

5.115 

4.875 

7.903 

7.228 

93.9 

94.0 

94.5 

95.0 

94.5 

93.0 

84.0 

94.0 

94.0 

82.3 

92.7 

92.2 

91.8 

83.9 

84.0 

93.0 

83.7 

95.0 

103.0 

105.0 

102.0 

909F 2 RVPs 

94.5 

93.2 

91.0 

96.0 

98.2 

98.0 

11.0 

10.8 

10.9 

11.1 

11.1 

10.7 

11.2 

11.0 

11.6 

10.9 

10.4 

10.4 

10.5 

10.4 

10.4 

45.9 

44.3 

44.4 

49.4 

43.9 

33.8 

48.6 

45.2 

67.0 

62.1 

61.1 

62.1 

63.2 

60.5 

61.1 

68.8 

69.5 

64.2 

65.3 

63.2 

56.6 

54.1 

57.9 

4.46 

1.37 

1.37 

1.43 

1.43 

1.42 

1.37 

1.35 

1.47 

1.42 

1.43 

1.45 

1.45 

1.40 

1.47 

1.43 

1.45 

1.45 

1.38 

1.43 

1.43 

1.40 

1.38 

17.00 

16.00 

28.00 

32.00 

40.00 

44.00 

28.00 

42.00 

25.00 

57.00 

56.00 

32.00 

50.00 

52.00 

58.00 

24.00 

25.00 

50.00 

28.00 

45.00 

40.00 

38.00 

42.00 

Dispensed Temperature = 669F 

66.5 

67.5 

5.029 

5.286 

74.0 

72.5 

73.9 

72.0 

10.4 

10.4 

10.4 

10.4 

11.3 

11.4 

10.5 

10.5 

49.3 

54.3 

53.2 

50.7 

89.3 

82.4 

52.8 

55.5 

1.40 

1.42 

1.38 

1.38 

1.63 

1.63 

1.35 

1.37 

32.00 

30.00 

32.00 

30.00 

26.00 

21.00 

6.00 

5.00 
P.65 

l98 3 piy^ u t h Rfilian t 

851151 

851150 

851152 

851153 

851154 

851155 

845486 

845487 

845492 

845493 

851157 

851156 

851159 

851246 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

9.0 

9.0 

11.9 

11.9 

9.0 

9.0 

11.9 

11.9 

2.5. 

1.7 

10.0 

19.3 

14.1 

18.0 

1.5 

-1.5 

3.0 

1.3 

4.3 

4.0 

5.5 

5.6 

846410 

846413 

846454 

846453 

846412 

846452 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

2.7 

13.0 

-.9 

-2.0 

.5 

.5 

80.0 

81.8 

81.0 

80.0 

79.9 

81.0 

90.5 

91.5 ' 

89.0 

91.0 

68.0 

69.0 

68.0 

68.3 

850205 

850209 

850208 

850207 

850206 

850204 

11.9 

11.9 

11.9 

11.9 

11.9 

11.9 

6.265 

6.640 

6.439 

4.969 

5.316 

6.109 

5.577 

5.677 

6.839 

7.036 

3.763 

3.939 

5.299 

5.323 

82.5 

83.5 

91.0 

99.3 

94.0 

99.0 

92.0 

90.0 

92.0 

92.3 

72.3 

73.0 

73.5 

73.9 

84.3 

84.0 

89.0 

97.5 

94.0 

99.7 

86.5 

87.0 

88.3 

89.5 

73.2 

72.0 

77.5 

78.0 

1983 Buick SkylarK 

12.7 

10.7 

13.2 

.7 

-.5 

2.6 

850400 

850401 

850402 

850404 

850405 

11.9 

11.9 

11.9 

11.9 

11.9 

11.2 

11.8 

U.O 

1.0 

1.8 

90.5 

85.0 

94.3 

93.5 

92.0 

92.0 

80.0 

81.0 

78.8 

91.8 

92.5 

89.4 

80.8 

79.2 

80.5 

90.8 

90.0 

850689 

850690 

850691 

850686 

350688 

11.9 

11.9 

11.9 

11.9 

11.9 

7.925 

6.471 

7.540 

7.353 

7.365 

7.708 

93.2 

98.0 

93.4 

91.5 

92.5 

92.5 

92.2 

91.0 

91.9 

90.0. 

90.6 

94.3 

1984 Chevrolet Celebrity 

9.8 

10.0 

9.8 

9.6 

9.5 

10.1 

10.4 

9.9 

11.2 

11.2 

9.7 

9.8 

9.7 

9.9 

4.632 

4.596 

4.706 

6.333 

6.876 

6.080 

92.7 

91.7 

92.0 

92.5 

92.0 

92.0 

92.2 

92.0 

92.1 

96.0 

94.5 

94.0 

1983 LETT Crown Victoria 

7.448 

7.200 

7.558 

11.166 

10.500 

92.0 

91.0 

91.5 

91.8 

91.8 

61.4 

66.4 

63.1 

47.7 

50.5 

61.7 

58.0 

56.2 

76.6 

78.8 

36.5 

38.6 

51.4 

52.7 

1.32 

1.32 

1.30 

1.28 

1.48 

1.37 

1.92 

1.87 

3.12 

3.17 

1.30 

1.32 

1.28 

1.30 

16.00 

16.00 

32.00 

44.00 

32.00 

38.00 

38.00 

38.00 

42.00 

43.00 

6.00 

4.00 

12.00 

14.00 

13.4 

13.6 

13.7 

13.6 

13.7 

12.0 

95.0 

94.0 

94.2 

95.4 

94.2 

14.5 

13.2 

10.3 

-.1 

2.6 

81.7 

82.3 

82.3 

91.3 

89.7 

6.048 

5.813 

5.795 

7.916 

7.964 

96.2 

95.5 

92.6 

91.7 

92.3 

92.0 

93.0 

93.5 

93.2 

93.5 

106.2 

88.0 

103.3 

100.0 

100.9 

92.5 

3.75 

2.32 

2.15 

2.05 

2.05 

1.80 

28.00 

28.00 

26.00 

23.00 

20.00 

19.00 

13.6 

13.6 

13.6 

13.8 

13.7 

13.8 

15.4 

14.5 

15.4 

15.7 

15.6 

63.0 

62.5 

64.0 

87.4 

94.2 

83.9 

1.78 

1.78 

1.85 

1.95 

1.95 

1.93 

44.00 

38.00 

40.00 

58.00 

38.00 

36.00 

114.7 

104.4 

116.4 

175.3 

163.8 

«ia*- 1/4 Ton PicKup 1979 Chevrolet -J/1*

 iU" 

16.6 

16.6 

16.6 

16.7 

16.6 

100.4 

96.5 

96.2 

132.2 

132.2 

2.02 

1.90 

2.05 

2.30 

2.25 

2.33 

2.27 

2.30 

2.43 

2.58 

53.00 

51.00 

42.00 

34.00 

36.00 

32.00 

23.00 

28. OC 

38 .OC 

32.0C 
P.66 

1979 Dodge Truck W150 

QA n 18 2 120.0 2.47 46.00 

850988 U-9 ,Z 
P.67 

Appendix B 

Fuel Consumption Weighting Data 
HIGHWAY USE OF OASOLINE BY MONTHS - IMS 

fill ! FM IM CIUBBM HM 

I JW INllll l JW MTM-tMl U l m UllNI I TMU w-t* 

IT» H 

*t*Nk 

l*I U 

kut w 

klI f 0**1A 

DIIMAM 

WU(1I» 1 

IlfttttM 

I m . M cat. 

llO«I M 

LiMti * 

||AM*II 

i l l 1*011 

UMIA M 

||0M* 

|l*aU I 

IHIIKI I 

laaiiiJM * 

|«*I M 

IMIUA M 

MttAcaattTTI 

•ItalU I 

| BIUIMT A 

M I i t min t 

MIIMI 1 

MITM * 

MIIAU A 

MVMA 

MM NMVMI M 

Mw MMI I 

MW Mi l It * 

Hw vg u 

awt a CAioti M 

BMT I Min t 

M i a 

a u JUM M 

aaicoa 

MUITIUMI A 

• M M IM.M * 

(aula tuati M 

taaiM Mtat * 

Itultll t 

TIM t 

• t u 

atinoal 

viMiai * 

«*MIMT M 

w « < viitui * 

WIKOMIB 

WMMI M 

m a t 

M*utt*& i 

U 1*11 u 

toasuariiaa. tt 

•*taaat l l tacit 

T M Mt t 

aa 

MCIMM1 I I 

• l a ctat i 

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Referencej. Refueling 

— " rtf Vehicle * SAE 

study

 o f ^, j campion, 

Experimental Jt u Y Raym0nd J. 

.. "An

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Emissions/ ^ W ^ 7 6 - „ service Station Vapo^ 

PaPer No. 7603 ser ptocedure „ 

-Testing o^

 a

californi» * » M-J . Dougherty o £ 

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: svstem OV. 1 " Memorandum « ° n 0l l 

C ° " " W " Tecnn^sear=n Department, 

SiA/a-"- •«• „,„„ s u -SP-E 

..Expansion °*60/3.76-006 U-SM«*li»«,JS.VV97S . t v sy stem Certified 0

" 

IcTD. September ^ ^ R^ 6 Jun ? I 982 ' 

• • • scr^^enta , -nnology . Ba lance„Sys -

^ r . . Service t Sta^ r s t R e O , r ^o. g . neerin g 

Hoonnauser " v , 7 6 . Measuring V ^ 

company. W1* * I O °

eaU

,L «

7 6 ' JUl Y 

"Evaluation ot Ucatl o . i No. ^ 

fuelin g Emissions. Recovery, ^f. l 2 , 1914, 

R

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ral i

 forn^ -

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 Research ana 

7- ^"nc e Diamond Ba« • £» „ Divis-n , 

System *«\°TMiiel d Company " ° 

feSiSi^" - " 7 ^ _ l e Development «-„ . SR E 

••vapor M<=° v

c

etY

H .J. «

l I "e s ' 

.esti ^ •* 3 .rM aS-' , W '

4

- . Ef£ec t tne £-£,* . 

— J 0- ... Study o L -ria D leS g -^mo D iles . . 

-ft-pd During t» placement 

Vapor *^te d ig75 .

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n

P

d uB from 

CEA-21. May i°» wffic ienc y

 o t

 , Memorandum 

•«; Control

 Eff * T s

 » Technical > Con.panY

 o r 

"Vapor

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 Stations, Un i o n 0 1 1 

1 0

 * a t TWO Service Departm ent , 

Systems a t ReS earc » 

M^J. ° o U f Teptem.e r 22, 1975. Em ission a «* 

California , Sep Emis sio n W* '

 stat ion . Hay 

Pollutio n ,* Exxon R e" , , IQ75 . 

MM^ M^rssrcA.. -.« -

California. 
P.72 

-59-

12. "Air Pollution Emission Test: Emissions from 

Gasoline Marketing Operations at Standard Oil of California 

Retail Station, Davis, California," U.S. EPA, OAWM, OAQPS, EMB, 

May 1975. 

13. "On-Board Control of Vehicle Refueling Emissions: 

Demonstration of Feasibility," API Publication No. 4306, 

October 1978. 

14. "Vapor Control Concepts," M.W. Lieferman, in 

"Vehicle Refueling Emissions Seminar," API Publication No. 

4222, December 1973. 

15. "A Chronic Inhalation Study With Unleaded Gasoline 

Vapor," Journal of the American College of Toxicology, American 

Petroleum Institute, 1984. 

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