# Light

- Duty Automotive T echnology and

Fuel Economy T rends:

1975 through 2007

A p p e n d i x A : D a t a b a s e D e t a i l s a n d

C a l c u l a t i o n M e t h o d s

Compliance and Innovative Strategies Division

and

T ransportation and Climate Division

Office of T ransportation and Air Quality

U.S. Environmental Protection Agency

NO TICE

T

his tec hnical report does not necessarily represent final EP A decisions or

positions. It is intended to present tec hnical analy sis of issues using dat a

that are cur rently a v ailable. T he purpose in the release of suc h reports is to

f acilit ate the e x

c

hange of tec hnical inf ormation and to inf orm the public of

tec hnical de v elopments.

EP A420-R-07-008

September 2007

## Harmonically Averagin g Fuel Economy Values

Di m e nsionally, fuel econom y is m iles divi ded by gallons. Then, presented with m ore

than one fuel econom y value, an approach to av eraging the values is to com pute the result by

determ ining the to tal m i les trav eled a nd di viding that by the total gallons used.

Exam ple: A motorist’s fuel econom y log for May shows that 704 m iles were

accum ulated around tow n in which the fuel econ o m y was 16 mpg, and one 216 m ile highway

trip was taken on which the fuel econom y was 24 mpg. W h at is the aver age fuel economy for

May ?

The total m i les are 704 + 216 = 920. The to tal gallons thus are 704 / 16 = 44 plus

216 / 24 = 9 or a total of 53 gallons. The aver age m pg is 920 / 53 = 17.4 m pg. Notice that the

arithm etic average of the two fuel econom y val u es (16 + 24) / 2 = 20 m pg gives an individual

result tha t is higher than the to tal m i les/to tal g allons result.

Even if the around-town m iles traveled and th e highway trip m iles traveled were the sam e

(460 m iles), the average fuel economy would not be 20; it would be 19.2 mpg. This is because

in the tota l m iles/tota l g allons appro ach, fue l consumption is arithm etically averaged, but fue l

economy is harm onically averaged, so for the se cond exam ple (equal tr ip distances), the

calculation would be:

Average MPG = 2 / (1/16 + 1/24) = 19.2 MPG,

which is th e sam e as arithm etically a v eraging the two fuel consum ption values.

A specific exam ple of this type of averaging approach is shown in the calculation of the

overall average fuel eco nom y using the EPA “city” (MPG C 

## ) and EPA “highway” (M PG H 

## ) fuel

econom y va lues.

Average MPG = Total M iles

Total Gallons

= _____Total Miles____________

City Gallons + Highway Gallons

= _____Total Miles______________________________

City Miles/City MPG + Highway Miles/Highway MPG

EPA420-R-07-008 A-1 Appendix A

## Now, if city m iles are 55 percen t of total m iles an d highway m iles are the rem aining 45

percen t, af te r divid i ng b y tota l m iles,

Average MP G = 1__________

(.55/MPG C 

## ) + (.45/MPG H 

## )

and this average m pg would represen t a com posite m pg value based on the 55% city/45%

highway driving in this exam ple. This 55% city /45% highw ay weightin g is the m etr ic in this

report for laboratory compos ite fuel econom y va lues.

The sam e approach can be used when th e average mpg of a gr oup of vehicles with

different m p g values is to be calculated. S uppose a fleet of 100,000 vehicles is m a de up of two

classes, one of 70,000 vehicles whose fuel econo my is 10 m p g and the other of 30,000 vehicles

whose fuel econom y is 14 m pg. Each vehicle in the fleet is assum e d to travel the same num ber

of

m iles ( M ),

Total Miles = 100,000 M

Total Gallons = 70,000 M / 10 + 30,000 M / 14

and the average fuel eco nom y is:

Average Fuel Econom y = 1

.7/10 + .3/14

= 10.9 m pg

where .7 an d .3 are th e relative shares of each ve hicle clas s in the fleet. Notice th at, again, th e

arithm etic average of the class fuel econom y va lues (10 + 14)/2 = 12 m pg is higher.

In general, som e for m of a weighted ha rm onic mean m u st be used when averaging

different fuel econom y values in order to m aintain m athem atical integrity.

EPA420-R-07-008 A-2 Appendix A

## Estimated and Final Sales Data

Table A-1 com pares average laborator y 55/45 fuel econom y for m odel years 1998

through 2005 at three points in tim e, and for MY2006 at two points in tim e:

(1) an in itial estim ate determ ined early in each m odel year using just pro j ected sales ;

(2) a revised estim ate determ ined by using tr ade publica tion sales da ta th at were

obtained after the end of each m odel year, but b e fore the final CAFE data were

subm itted by autom akers to the Fed e ral Governm ent; and

(3) final fuel econom y va lues determ ined from CAFE com p liance data provided

by the m a nufacturers to the Federal Govern m e nt after the end of the m o del year.

The final car plus truck fuel econom y values have varied from .4 m pg lower to .3 m p g

higher com p ared to the o r igin al es tim ates bas ed ex clusiv ely o n estim ated sales. The revised car

plus truck value for MY2006 in this report is 0.7 mpg higher than the initial estim ate for 2006 in

last year’s report, which suggests that sustained, higher gasoline pr ices have led to som e changes

in consum er dem a nd relative to what m a nufact urers expected prior to the start of 2006.

Table A-1

**Comparison of Laboratory 55/45 MPG**

**Model Initial**  **Revised Final** 

**Year Estimate**  **Estimate Value** 

**Cars** 1998 28.6 28.6 28.5

1999 28.1 28.2 28.1

2000 28.1 28.3 28.2

2001 28.3 28.3 28.4

2002 28.5 28.5 28.6

2003 29.0 28.9 28.9

2004 28.7 28.9 28.9

2005 28.9 29.2 29.5

2006 28.8 29.2 ***

**Trucks** 1998 20.6 20.6 20.9

1999 20.3 20.4 20.5

2000 20.5 20.5 20.8

2001 20.3 20.4 20.6

2002 20.4 20.3 20.6

2003 20.8 20.9 20.9

2004 20.9 20.9 20.8

2005 21.3 21.2 21.4

2006 21.5 21.9 ***

**Both** 1998 24.4 24.4 24.5

1999 23.8 24.0 24.1

2000 24.0 23.9 24.3

2001 23.9 24.0 24.2

2002 24.0 23.9 24.1

2003 24.4 24.2 24.3

2004 24.4 24.4 24.0

2005 24.6 24.6 24.8

2006 24.6 25.3 ***



### EPA420-R-07-008 A-3 Appendix A

## Use of 3-Year Moving Averages

Use of the three-y ear m oving averages, which effectively smooth the tr ends, results in an

im prove m ent in discrim i nating r eal trends from what m i ght be rela tive l y s m all year-to

- year

variations in the data. For this report, as shown in Table A-2, these three-year m oving averages

are tabulated at the m i dpoint. For exam pl e, the m i dpoint for m odel years 2002, 2003, and 2004

is MY2003.

Table A-2

**Light-Duty Vehicle Laboratory Fuel Economy and Truck Sales Fraction**

**Actual Data Three-Year Moving Average** 

**55/45 Fuel Economy**  **Truck 55/45 Fuel Economy**  **Truck**

**Year Cars**  **Trucks Both**  **Sales Cars**  **Trucks Both**  **Sales**

**Fraction Fraction** 

1975 15.8 13.7 15.3 0.194 ****   ** ** *****

1976 17.5 14.4 16.7 0.212 17.1 14.5 16.5 0.202

1977 18.3 15.6 17.7 0.200 18.5 15.1 17.6 0.213

1978 19.9 15.2 18.6 0.227 19.4 15.2 18.3 0.216

1979 20.3 14.7 18.7 0.222 21.1 16.0 19.8 0.205

1980 23.5 18.6 22.5 0.165 22.8 17.5 21.5 0.187

1981 25.1 20.1 24.1 0.173 24.8 19.7 23.7 0.178

1982 26.0 20.5 24.7 0.197 25.7 20.5 24.5 0.197

1983 25.9 20.9 24.6 0.223 26.1 20.6 24.6 0.219

1984 26.3 20.5 24.6 0.239 26.4 20.6 24.7 0.239

1985 27.0 20.6 25.0 0.254 27.0 20.8 25.1 0.258

1986 27.9 21.4 25.7 0.283 27.6 21.2 25.5 0.272

1987 28.1 21.6 25.9 0.278 28.2 21.4 25.8 0.286

1988 28.6 21.2 25.9 0.298 28.3 21.2 25.8 0.294

1989 28.1 20.9 25.4 0.307 28.2 20.9 25.5 0.302

1990 27.8 20.7 25.2 0.302 28.0 21.0 25.3 0.310

1991 28.0 21.3 25.4 0.322 27.8 20.9 25.2 0.319

1992 27.6 20.8 24.9 0.334 27.9 21.0 25.1 0.339

1993 28.2 21.0 25.1 0.360 28.0 20.8 24.8 0.366

1994 28.0 20.8 24.6 0.404 28.2 20.7 24.8 0.381

1995 28.3 20.5 24.7 0.380 28.2 20.7 24.7 0.395

1996 28.3 20.8 24.8 0.400 28.3 20.7 24.7 0.401

1997 28.4 20.6 24.5 0.424 28.4 20.8 24.6 0.424

1998 28.5 20.9 24.5 0.449 28.4 20.7 24.4 0.441

1999 28.2 20.5 24.1 0.449 28.3 20.7 24.3 0.449

2000 28.2 20.8 24.3 0.449 28.3 20.6 24.2 0.453

2001 28.4 20.6 24.2 0.461 28.4 20.6 24.2 0.465

2002 28.6 20.6 24.1 0.485 28.7 20.7 24.2 0.481

2003 28.9 20.9 24.3 0.496 28.8 20.8 24.1 0.500

2004 28.9 20.8 24.0 0.520 29.1 21.0 24.4 0.504

2005 29.5 21.4 24.8 0.495 29.2 21.3 24.7 0.492

2006 29.2 21.9 25.3 0.461 29.4 21.8 25.2 0.482

2007 29.4 22.1 25.3 0.490   ** **   ** ***



### EPA420-R-07-008 A-4 Appendix ATable A-2 (Continued)

**Light-Duty Vehicle Adjusted Fuel Economy**

**Cars**

**Model Each Year’s Data**  **3 Year Moving Avg.**

**Year CITY**  **HWY COMP**  **CITY HWY**  **COMP**

1975 12.3 15.2 13.5   ** **  

1976 13.7 16.6 14.9 13.4 16.3 14.6

1977 14.4 17.4 15.6 14.5 17.6 15.8

1978 15.5 19.1 16.9 15.3 18.5 16.6

1979 15.9 19.2 17.2 16.5 20.2 18.0

1980 18.3 22.6 20.0 17.8 21.8 19.4

1981 19.6 24.2 21.4 19.3 24.1 21.2

1982 20.1 25.5 22.2 19.8 25.1 21.9

1983 19.9 25.5 22.1 20.1 25.7 22.2

1984 20.2 26.0 22.4 20.3 26.1 22.5

1985 20.7 26.8 23.0 20.7 26.8 23.0

1986 21.2 27.6 23.7 21.0 27.4 23.5

1987 21.2 27.7 23.8 21.3 27.8 23.9

1988 21.4 28.2 24.1 21.2 27.9 23.9

1989 20.9 27.9 23.7 20.9 27.8 23.7

1990 20.5 27.5 23.3 20.6 27.7 23.5

1991 20.5 27.6 23.4 20.3 27.5 23.3

1992 20.0 27.5 23.1 20.2 27.6 23.3

1993 20.3 27.9 23.5 20.1 27.7 23.3

1994 20.0 27.7 23.3 20.1 27.9 23.4

1995 20.0 28.1 23.4 19.9 27.9 23.3

1996 19.8 28.0 23.3 19.9 28.0 23.4

1997 19.8 28.0 23.4 19.8 28.0 23.4

1998 19.7 28.0 23.4 19.6 27.8 23.2

1999 19.4 27.5 23.0 19.5 27.6 23.1

2000 19.3 27.3 22.9 19.3 27.4 23.0

2001 19.4 27.3 23.0 19.4 27.3 23.0

2002 19.4 27.2 23.1 19.4 27.3 23.1

2003 19.5 27.5 23.2 19.4 27.4 23.2

2004 19.3 27.4 23.1 19.4 27.5 23.3

2005 19.6 27.6 23.5 19.4 27.5 23.3

2006 19.4 27.5 23.3 19.5 27.6 23.4

2007 19.5 27.6 23.4 ** **   ** **



### EPA420-R-07-008 A-5 Appendix ATable A-2 (Continued)

**Light-Duty Vehicle Adjusted Fuel Economy**

**Trucks**

**Model Each Year’s Data**  **3 Year Moving Avg.**

**Year CITY**  **HWY COMP**  **CITY HWY**  **COMP**

1975 10.9 12.7 11.6   ** **  

1976 11.5 13.2 12.2 11.7 13.3 12.3

1977 12.6 14.1 13.3 12.2 13.7 12.8

1978 12.4 13.7 12.9 12.4 13.6 12.9

1979 12.1 13.1 12.5 13.0 14.4 13.6

1980 14.8 17.1 15.8 14.1 15.9 14.9

1981 16.0 18.6 17.1 15.7 18.2 16.7

1982 16.3 19.0 17.4 16.3 19.1 17.4

1983 16.5 19.6 17.8 16.3 19.3 17.5

1984 16.1 19.3 17.4 16.3 19.4 17.6

1985 16.2 19.4 17.5 16.4 19.6 17.7

1986 16.8 20.2 18.2 16.6 20.0 18.0

1987 16.8 20.5 18.3 16.6 20.3 18.1

1988 16.2 20.2 17.9 16.3 20.2 17.9

1989 15.9 19.8 17.6 15.9 19.9 17.6

1990 15.6 19.8 17.4 15.8 20.0 17.6

1991 15.9 20.3 17.8 15.7 20.0 17.5

1992 15.5 19.9 17.4 15.6 20.1 17.5

1993 15.5 20.1 17.5 15.4 19.9 17.3

1994 15.3 19.7 17.2 15.2 19.7 17.2

1995 15.0 19.5 17.0 15.1 19.7 17.1

1996 15.1 19.9 17.2 15.0 19.6 17.0

1997 14.8 19.5 17.0 14.9 19.7 17.1

1998 14.9 19.8 17.1 14.8 19.5 16.9

1999 14.6 19.2 16.7 14.7 19.5 16.9

2000 14.7 19.4 16.9 14.6 19.2 16.8

2001 14.6 19.1 16.7 14.6 19.2 16.8

2002 14.4 19.1 16.7 14.5 19.1 16.8

2003 14.6 19.3 16.9 14.4 19.2 16.8

2004 14.3 19.2 16.7 14.5 19.4 16.9

2005 14.6 19.8 17.2 14.6 19.7 17.2

2006 15.0 20.2 17.6 14.9 20.1 17.5

2007 15.1 20.4 17.7 ** **   ** **



### EPA420-R-07-008 A-6 Appendix ATable A-2 (Continued)

**Light-Duty Vehicle Adjusted Fuel Economy**

**Cars and Trucks**

**Model Each Year’s Data**  **3 Year Moving Avg.**

**Year CITY**  **HWY COMP**  **CITY HWY**  **COMP**

1975 12.0 14.6 13.1   ** **  

1976 13.2 15.7 14.2 13.0 15.6 14.1

1977 14.0 16.6 15.1 13.9 16.6 15.0

1978 14.7 17.5 15.8 14.5 17.2 15.6

1979 14.9 17.4 15.9 15.6 18.6 16.8

1980 17.6 21.5 19.2 16.9 20.3 18.3

1981 18.8 23.0 20.5 18.5 22.8 20.2

1982 19.2 23.9 21.1 19.0 23.6 20.8

1983 19.0 23.9 21.0 19.1 23.9 21.0

1984 19.1 24.0 21.0 19.1 24.1 21.1

1985 19.3 24.4 21.3 19.4 24.5 21.4

1986 19.8 25.0 21.8 19.6 24.9 21.7

1987 19.8 25.3 22.0 19.7 25.2 21.9

1988 19.6 25.2 21.9 19.5 25.1 21.7

1989 19.1 24.8 21.4 19.1 24.9 21.5

1990 18.7 24.6 21.2 18.9 24.7 21.3

1991 18.8 24.7 21.2 18.6 24.6 21.1

1992 18.2 24.4 20.8 18.4 24.5 21.0

1993 18.2 24.4 20.9 18.1 24.2 20.7

1994 17.8 23.8 20.4 17.9 24.1 20.6

1995 17.7 24.1 20.5 17.7 24.0 20.4

1996 17.6 24.0 20.4 17.6 23.9 20.3

1997 17.4 23.6 20.1 17.4 23.7 20.2

1998 17.2 23.6 20.1 17.1 23.4 20.0

1999 16.9 23.0 19.7 17.0 23.2 19.8

2000 16.9 23.0 19.8 16.9 23.0 19.7

2001 16.8 22.8 19.6 16.8 22.8 19.6

2002 16.6 22.5 19.4 16.7 22.7 19.5

2003 16.7 22.7 19.6 16.6 22.6 19.4

2004 16.3 22.4 19.3 16.6 22.7 19.6

2005 16.8 23.1 19.9 16.7 23.0 19.8

2006 17.1 23.5 20.2 17.0 23.4 20.1

2007 17.1 23.6 20.2 ** **   ** **



### EPA420-R-07-008 A-7 Appendix A

## Vehicle Cla ssification Exceptions

The truck s i ze classification sch em e used in th is report is bas e d prim arily on published

wheelbase data. For cars, vehicle classification as to vehicle type, size class, and m a nufacturer/

origin generally follows fuel economy label, Fuel Economy Guide , and fuel econom y standards

protocols; exceptions are listed in T a ble A-3. T h e class i fication of a veh i cle for this report is

based on the authors ’ en gineering ju dgm ent and is not a replacem ent for definition s u sed in

im plem enting autom o tive standa rds legislation

.

Table A-3

**Group/Manufacturer/Vehicles Years**  **Are Classified As:**

DC: Chrysler Colt 4WD Wagon All Small Wagon

DC: Chrysler Colt Vista All Small Van

DC: Chrysler Pacifica All Large Wagon

DC: Chrysler PT Cruiser All Small Wagon

DC: Chrysler PT Cruiser Convertible All Subcompact

DC: R-Series All Large Wagon

DC: Chrysler Summit Wagon All Small Van

DC: Dodge Ramcharger All Car

DC: Dodge Magnum All Midsize Wagon

DC: Eagle 4WD Wagon All Car

Ford: Ford Pinto Van All Car

Ford: Volvo V70 XC All Midsize Wagon

GM: HHR All Small Wagon

GM: Isuzu Oasis All Midsize Van

GM: Pontiac Vibe All Small Wagon

Toyota: Lexus RX300 All Midsize SUV

Toyota: Matrix All Small Wagon

VW: Audi Allroad All Midsize Wagon

Other: Subaru 4WD Sedans/Wagons All Cars

Other: Subaru Forester All Small SUV

Other: Subaru Baja All Small Pickup

Other: Suzuki X-90 All Small SUV

Other: Mitsubishi Expo All Small Van

Other: Mitsubishi Space Wagon All Small Van

EPA420-R-07-008 A-8 Appendix A

## Ne w Methodology for Adjusted Fuel Economy Values

for Model Years 1986-2007

On Dece m b er 27, 2006, EPA published new re gulations that changed the m e thodology

for calculating the city and highway fuel econom y label estimates for new passenger cars and

light truck s (71 Federal Register 778 72). The new m e thodology will pro vide fuel econom y

estim ates to consum ers that better reflect real world fuel econo m y. The new m e thodology

incorporates test data that dir ectly account for several im portant factors that affect fuel econom y

in the real w o rld, such as high speeds

, aggress i ve acceleration s and decele rations, the use of air

conditioning, and operation in cold temperatures, and indirectly accounts f o r a num ber of other

factors th at are not refl e c ted in EPA test d a ta.

These new vehicle fuel econom y label cha nges take effect beginning with the 2008

model year. For m odel years 2008-2010, m a nufacturers will have two options for calculating

city and highway fuel econom y labels: 1) us ing vehicle-specific “5-cy c le” (Federal T e st

Procedure f or urban stop-and-go driving, Highway Fuel Econom y Test for rural driving, US06

test for h i gh speeds and aggressiv e driving, SC O3 test for air condition i ng operation, and cold

FTP test for cold tem p erature op eration) fuel eco nom y test data in “com posite” equations that

calculate vehicle-specific city and highway fuel econom y va lues using w e ighting factors for data

from each of the 5 EPA test cycles, o r 2) us ing an industry

- average “m pg-based” m e thod, which

yields m pg-based adjustm e nts based on a regression of recent 5-cycle fuel econom y da ta for the

industry as a whole. Beginning in 2011, m a nufact urers m u st use the 5-cycle m e thod. For m o re

details on the derivation of these options, the sp e cif ic equa tio ns that allow an autom aker to

calcu late n e w label va lu es using e ith er the v ehic l e-spec if ic 5- cycle test d a ta or the ind u stryaverage m pg-based app r oach, and the im pact of these ch ang e s on averag e fuel econo my label

values, see the Pream ble to the new regul ations (71 Federal Register 77881-77893).

EPA is m a king significant changes in this 2007 report in how adjusted (ADJ) fuel

econom y va lues for m odel years 1986 through 2007 ar e calculated to reflect the new EPA fuel

econom y label m e thodology. These changes affect every table and figure in the report that

involve adjusted fuel econom y data. Accordingly, adjusted fuel econom y values for 1986 and

later m odel years should not be compared with the correspo nding va lues from previous reports in

this series. Specifically, the new adjusted fuel econom y values for 1986-2007 in this report

differ from those in previous reports as explained below.

• For m odel years 2005-2007, EPA now calculate s adjusted fuel econom y values for

individual models in the fuel economy tre nds database using the following city and

highway “mpg-based” equations from th e EPA fuel econom y labeling rulem a king:

1

New ADJ CITY = -------------

----------------- --------------

0.003259 + 1.1805

LAB CITY

EPA420-R-07-008 A-9 Appendix A

## 1

New ADJ HW Y = ---------------

--------------- ------------

0.001376 + 1.3466

LAB HWY

Calculating fleetwide adjust ed city and highway fuel economy values for a given

model year requires a harmonic, sales-weighted average of all of the adjus t ed city and

highway fuel econom y values for individual m o dels.

The above equations yield a greater downw ard adjustm e nt for higher fuel econom y

vehicles than for lower fuel econom y vehicl es. For exam ple, com p ared to the older

fuel economy label m e thodology, a 15 m pg city value will be reduced by an

additional 10%, while a 50 m pg city value wi ll be reduced by an additional 18%.

Likewise, a 20 m pg highway value will b e reduc e d by an additiona l 7%, w h ile a 50

mpg highway value will be reduced by an additional 11%. E P A projected an overall

average fleetwide adjustm e nt of 11% lower for city fuel econom y and 8% lower for

highway fuel econom y, beyond that in the older label adjustm e nt m e thodology that

has been used in previous reports in this se ries. T hese factors can be used to convert

older adjusted fuel econom y values to th e new adjusted fuel econom y val ues for the

curren t fleet as a whole, but would not be appropriate f actors to use for individual

models or for a future fleet with different m pg characteristics.

This report seldom uses separate city and highway fuel economy values, but typically

uses the composite city/highway fuel econom y value. In the past, this report has used

a 55% city/45% highway weighting, the we ighting used in the CAFE compliance

program

. The analysis of real world driving activity underlying the new fuel

econom y label m e thodology assum e d a “speed cutpoint” of 45 m iles per hour to

differentiate between city and highway dr iving (71 Federal Regi ster 77904). Based

on this speed cutpoint, the correct w e ighti ng for correlating the new city and highway

fuel economy values with real world dr iving, on a m iles driven basis, is 43%

city/57% highway. Accordingly, this we ighting is now used for all adjusted

com posite city/highway f u el econom y valu es beginning with the 2005 m o del year.

The appropriate fleetwide f actors to convert laboratory or older adjusted f uel

econom y va lues to new adjusted fuel econom y values are dependent on the city fuel

econom y-to-highway fuel econom y ratios in th e f l eet. On average, for the current

fleet, com b ining the 11% lower adjustm e nt for city fuel econom y, the 8% lower

adjustm e nt for highway fuel econom y, and the shift to the 43 % city/57% highway

weighting, the new adjustm e nt for city/hi ghway com posite fuel econom y values is

6% lower than that used in the older la bel adjustm e nt m e thodology. This 6% lower

value is the average im pact for a fleet with the mpg and city f u el econom y-tohighway fuel econom y characteristics of the current fleet, and would not be the

appropriate value for individual m odels, part ial fleet segm ents, or for future fleets

with different m pg and city fuel econom y-to-highway fuel econom y distributions.

EPA420-R-07-008 A-10 Appendix A

## • For m odel years 1986 through 2004, EPA now ca lculates adjusted fuel econom y

values based on the assumption that the im pact s of the factors that have led to lower

real world fuel econom y have occurred in a gradual (i.e., linear) m a nner over the 20

years from 1986 through 2005. On April 6, 1984, EPA published regulations that

established the older fuel econom y label ad justm e nt factors of 0.9 for city fuel

econom y and 0.78 for highway fuel econom y that took effect for m odel year 1985

vehicles (49 Federal Regist er 13832). EPA believes that these adjustm e nt factors

were appropriate through th e 1985 model year. EPA has not attem p ted to perform a

year-by

- year analys is to determ ine th e ex tent to which the many relevant factors

(including highway speed lim its, m o re aggr essive driving, vehi cle horsepower-toweight ratio, suburbanization, congest ion, use of air cond ition i ng, gasolin e

com position, et al) that have affected real world fuel econom y since 1985 have

changed over tim e. Rather, EPA has m a de the simplifying, but we think reasonable,

assum p tion that the colle ctive im pact of th ese changes has been a linearly increasing

im pact over the 20 years from 1986 through 2005. Using the equations shown above

for individual m odels, EPA has assum e d 1/20 of the fully phased-in downward

adjustm e nt for city and highway values w ould be reflected in the 1986 data, 2/20 of

this adjustm e nt would be reflected in the 1987 data, etc., up to 19/20 of this

adjustm e nt in 2004 and the full adjustm e nt in 2005, 2006, and 2007. Likewise, EPA

has assum e d the 55/45 city/highway wei ghting changes to a 43/57 city/highway

weighting in a linear fashion over the 1986 to 2005 tim e period as well. As discussed

above, the average fleetwide com posite c ity/highway fuel econom y values for 2005-

2007 are 6% lower than the com posite city/h ighw ay fuel econom y value calculated

with the o l d er adjus t m ent f actors.

To generate precise adjusted city, highw ay, or com posite fuel econom y values for

individual models or for future fleetwide averages with different m pg or city fuel econom y-tohighway fuel econom y ratios than the current fleet, it is essential to use the above equations to

calculate adjusted city and hi ghway fuel econom y values for i ndividual models, then use the

43% city/57% highway weighting to generate an adjusted co mposite fuel econom y va lue for

individual models, and then calcu late the harm onically sale s- weight ed av erage of the individu al

models to yield the average com posite fuel economy for the fleet as a whole. Alternatively, for a

first-order estim ate of generic fl eetwide factors that one could us e to co nvert values from the

historic fuel econom y trends database to new ad justed fuel econom y levels, see the factors in

Table A-4, which are based on the m pg and c ity f uel econom y-to-highway fuel economy

characteristics of the current fleet. F or ex am ple, the industry-wide adjusted com posite

city /highway fuel econo my value for m odel y ear 1986 in this year’s report, which will be

reported as ADJ COMP, is about .997 (1.0 m i nus 0.003, where 0.003 equals 0.3%, and the latter

is equal to 6% divided by 20) tim es the adjusted com posite city/highway f uel econom y value, or

ADJ 55/45, from previous reports in this series

. Likewise, the sam e industry-wide ADJ COMP

value f o r 19 86 can be ap proxim ated by m u ltiply ing the labo r atory com posite 55 /45 va lue f o r

1986 by 0.851. The industry-wide ADJ COMP fuel economy values for m odel years 2005-2007

in this year’s report are all eq ual to 0.80 tim es the laboratory com posite 55/45 values. Table A-5

provides a com parison of adjusted composite fuel econom y va lues, for cars and trucks com bined,

using both the older fuel econom y label m e thodology th at has been used in past reports in this

series as well as the new fuel economy label m e thodology described above and used for the first

EPA420-R-07-008 A-11 Appendix A

## tim e in this report. For data from M Y 2003-2007, the adjusted fuel economy values using the

new EPA fuel econom y m e thodology ar e 1.1-1.3 m pg lower than they would be using the older

EPA fuel econom y label m e thodology.

No changes have been made in the way EPA calculates adjus t ed fuel econ o m y values for

1975-1985. For these m odel years, EPA still us es the 0.9 city/0.78 high way fuel econom y

adjustm e nts established in 1984, al ong with the 55% city/45% hi ghway weighting factor. EPA

believes that this m e thodology was appropriate f o r the late 1970s and early 1980s and is not

m a king any changes to adjusted fuel econom y va lues for 1975 through 1985.

Finally, no changes have been m a de in the la boratory (LAB) fuel econom y values in this

report. The laboratory city value remains th e fuel econom y va lue over the EPA Federal Test

Procedure, the laboratory highway value rem a in s the fuel eco nom y value over the EP A Highway

Fuel Economy Test, and the laboratory 55/45 is a weighted value of these two tests, w ith a 55%

weighting of the Federal Test Procedure and a 45% weighting of the Highway Fuel Econom y

Test. The laboratory 55/45 values are used for CAFE com pliance, in conjunction with

alternative fuel vehicle credits and test pr ocedu r e adjustm e nts. Because th e underly i ng

m e thodology for generating and reporting the labora tory fuel econom y va lues have not changed

since this series began in the m i d-1970s, these va lues provide an excellent basis with w hich to

com p are long-term fuel econom y trends from the perspective of vehicle design, apart from the

factors th at affect real w o rld fuel eco nom y that are reflected in the adju sted fuel econo my values.

EPA420-R-07-008 A-12 Appendix A

## Table A-4

Approximate Factors for Converting Industry-Wi de Fuel Economy Values from Previous

Reports to the Ne w Adj u sted Fuel Economy Values in this 2007 Report

Factors to convert older ADJ to new ADJ Factors to convert LAB to new ADJ

CITY HWY 55/45 CITY HW Y 55/45

1975-1985 1.00 1.00 1.00 .900 .780 .854

1986 .995 .996 .997 .895 .777 .851

1987 .989 .992 .994 .890 .774 .849

1998 .984 .988 .991 .885 .771 .846

1989 .978 .984 .988 .880 .768 .843

1990 .973 .980 .985 .875 .765 .841

1991 .967 .976 .982 .870 .762 .838

1992 .962 .972 .979 .865 .759 .835

1993 .956 .968 .976 .860 .756 .832

1994 .951 .964 .973 .855 .753 .830

1995 .945 .960 .970 .850 .750 .827

1996 .940 .956 .967 .845 .747 .824

1997 .934 .952 .964 .840 .744 .822

1998 .929 .948 .961 .835 .741 .819

1999 .923 .944 .958 .830 .738 .816

2000 .918 .940 .955 .825 .735 .814

2001 .912 .936 .952 .820 .732 .811

2002 .907 .932 .949 .815 .729 .808

2003 .901 .928 .946 .810 .726 .805

2004 .896 .924 .943 .805 .723 .803

2005 .890 .920 .940 .800 .720 .800

2006 .890 .920 .940 .800 .720 .800

2007 .890 .920 .940 .800 .720 .800

Im portant Notes for Table A-4:

1. Multip lying the factors above tim e s the a pprop riate valu es from previous reports

approxim a tes the new adjusted (ADJ) fuel economy values in this 2007 report.

2. These factors are first-order approxim ations relevant only for industry-wide fuel econom y

values for the 1986 through 2007 timefram e

.

EPA420-R-07-008 A-13 Appendix A

## 3. Precise estim ates for individual models requ ire the use of the m pg-based equations for ADJ

CITY and ADJ HWY in the text as w e ll as a linear phase-in, over the 1986 to 2005 tim e period,

for both the mpg-based equations and the change from a 55/45 city/highw ay weighting to a

43/57 city/highway weighting.

4. These approxim a tions would yield the largest e rror for individual m o dels or fleets with high

mpg and/or high city fuel econom y- to-highway fuel econom y ratios.

Table A-5

Comparison of “Old” and “Ne w ” Adjusted Composite F u el Economy Values,

for Cars and Trucks Combined, for 2003-2007

Cars and Trucks Combined

Model

Year “Old”

Adjusted

Composite “Ne w ”

Adjusted

Composite

2003 20.7 19.6

2004 20.5 19.3

2005 21.2 19.9

2006 21.5 20.2

2007 21.5 20.2

Im portant Notes for Table A-5:

1. “Old” adjusted com posite fuel economy values are based on the EPA fuel econom y label

m e thodology used in previous reports in this series, i.e., 10% downward city adjustm e nt,

22% downward highway adjustm e nt, and a 55% city/45% highway weighting factor.

2. “New” adju sted com posite fuel econ om y valu es are based on the new EPA fuel econom y

label m e thodology, applicable to MY2008 vehicles and used for the first tim e in this

2007 report and described in the previous section.

3. The “new” adjusted composite fuel econom y va l ues for cars and trucks com bined are

approxim a tely 6% lower than the “old” adjust ed com posite fuel econom y values for cars

and trucks com bined. For cars only, the “n ew” adjusted composite fuel econom y val ues

would be more than 6% lower than the “o ld” values, while for trucks only, the “new”

adjusted composite fuel econom y va lues woul d be less than 6% lower than the “old”

values.

EPA420-R-07-008 A-14 Appendix A

## Comparison of EPA and NHTSA Data

Table A-6 com pares CAFE data reported by the National Highway Traffic Safety

Adm i nistration (NHTSA) with the adjusted and unadjusted (labor atory) com posite fuel econom y

data in this report. The NHTSA values in Tabl e A-6 are generally higher than the unadjusted or

laboratory mpg values due to di fferences in vehicle classification, test pr ocedure adjustm e nt

factors for cars and alternative fuel credits. Th e NHTSA data for MY1979 trucks in this table is

just for vehicles up to 6000 pound GVW ; but fo r all other years the NHTSA data includes

vehicles up to 8500 GVW. The NHTSA data for MY2006 is based on m i d-m odel year data.

The EPA da ta for all years in the table includes vehicles up to 8500 GVW. In addition, the EPA

data in the table is final through MY 2005, but prelim inary for MY2006 and MY2007.

Table A-6

**EPA Adjusted, Laboratory, and NHTSA CAFE Fuel Economy Values**

**by Model Year**

**Cars Trucks**  **Both Cars and Trucks**

**Model EPA**  **EPA NHTSA**  **EPA EPA**  **NHTSA EPA**  **EPA NHTSA** 

**Year Adj. Unadj. (CAFE) Diff.**  **Adj. Unadj. (CAFE) Diff. Adj. Unadj. (CAFÉ) Diff.** 

1975 13.5 15.8 n/a 11.6 13.7 n/a 13.1 15.3 n/a

1976 14.9 17.5 n/a 12.2 14.4 n/a 14.2 16.7 n/a

1977 15.6 18.3 n/a 13.3 15.6 n/a 15.1 17.7 n/a

1978 16.9 19.9 19.9 .0 12.9 15.2 n/a 15.8 18.6 19.9 1.3

1979 17.2 20.3 20.3 .0 12.5 14.7 18.2 3.5 15.9 18.7 20.1 1.4

1980 20.0 23.5 24.3 .8 15.8 18.6 18.5 -.1 19.2 22.5 23.1 .6

1981 21.4 25.1 25.9 .8 17.1 20.1 20.1 .0 20.5 24.1 24.6 .5

1982 22.2 26.0 26.6 .6 17.4 20.5 20.5 .0 21.1 24.7 25.1 .4

1983 22.1 25.9 26.4 .5 17.8 20.9 20.7 -.2 21.0 24.6 24.8 .2

1984 22.4 26.3 26.9 .6 17.4 20.5 20.6 .1 21.0 24.6 25.0 .4

1985 23.0 27.0 27.6 .6 17.5 20.6 20.7 .1 21.3 25.0 25.4 .4

1986 23.7 27.9 28.2 .3 18.2 21.4 21.5 .1 21.8 25.7 25.9 .2

1987 23.8 28.1 28.5 .4 18.3 21.6 21.7 .1 22.0 25.9 26.2 .3

1988 24.1 28.6 28.8 .2 17.9 21.2 21.3 .1 21.9 25.9 26.0 .1

1989 23.7 28.1 28.4 .3 17.6 20.9 21.0 .1 21.4 25.4 25.6 .2

1990 23.3 27.8 28.0 .2 17.4 20.7 20.8 .1 21.2 25.2 25.4 .2

1991 23.4 28.0 28.4 .4 17.8 21.3 21.3 .0 21.2 25.4 25.6 .2

1992 23.1 27.6 27.9 .3 17.4 20.8 20.8 .0 20.8 24.9 25.1 .2

1993 23.5 28.2 28.4 .2 17.5 21.0 21.0 .0 20.9 25.1 25.2 .1

1994 23.3 28.0 28.3 .3 17.2 20.8 20.8 .0 20.4 24.6 24.7 .1

1995 23.4 28.3 28.6 .3 17.0 20.5 20.5 .0 20.5 24.7 24.9 .2

1996 23.3 28.3 28.5 .2 17.2 20.8 20.8 .0 20.4 24.8 24.9 .1

1997 23.4 28.4 28.7 .3 17.0 20.6 20.6 .0 20.1 24.5 24.6 .1

1998 23.4 28.5 28.8 .3 17.1 20.9 21.0 .1 20.1 24.5 24.7 .2

1999 23.0 28.2 28.3 .1 16.7 20.5 20.9 .4 19.7 24.1 24.5 .4

2000 22.9 28.2 28.5 .3 16.9 20.8 21.3 .5 19.8 24.3 24.8 .5

2001 23.0 28.4 28.8 .4 16.7 20.6 20.9 .3 19.6 24.2 24.5 .3

2002 23.1 28.6 29.0 .4 16.7 20.6 21.4 .8 19.4 24.1 24.7 .6

2003 23.2 28.9 29.5 .6 16.9 20.9 21.8 .9 19.6 24.3 25.1 .8

2004 23.1 28.9 29.5 .6 16.7 20.8 21.5 .7 19.3 24.0 24.6 .6

2005 23.5 29.5 30.3 .8 17.2 21.4 22.1 .7 19.9 24.8 25.4 .6

2006 23.3 29.2 29.8 .6 17.6 21.9 22.2 .3 20.2 25.3 25.4 .1

2007 23.4 29.4 n/a 17.7 22.1 n/a 20.2 25.3 n/a



### EPA420-R-07-008 A-15 Appendix A