[Code of Federal Regulations]
[Title 40, Volume 29]
[Revised as of July 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR600.113-88]

[Page 899-900]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 600_FUEL ECONOMY OF MOTOR VEHICLES--Table of Contents
 
    Subpart B_Fuel Economy Regulations for 1978 and Later Model Year 
                       Automobiles_Test Procedures
 
Sec. 600.113-88  Fuel economy calculations.

    The Administrator will use the calculation procedure set forth in 
this paragraph for all official EPA tests. For the 1988 model year, 
manufacturers may choose to use this procedure or use the calculation 
procedure described in Sec. 600.113-78. However, once a manufacturer 
uses this procedure, it must be used for all subsequent tests. This 
procedure must be used by manufacturers for 1989 and later model years. 
The calculations of the weighted fuel economy values require input of 
the weighted grams/mile values for HC, CO and CO2 for both 
the city fuel economy test and the highway fuel economy test. 
Additionally, for tests of gasoline-fueled vehicles, the specific 
gravity, carbon weight fraction and net heating value of the test fuel 
must be determined. The city and highway fuel economy values shall be 
calculated as specified in this section. A sample appears in appendix II 
to this part.
    (a) Calculate the weighted grams/mile values for the city fuel 
economy test for HC, CO, and CO2 as specified in Sec. 86.144 
of this chapter. For tests of gasoline-fueled vehicles, measure and 
record the test fuel's properties as specified in paragraph (c) of this 
section.
    (b)(1) Calculate the mass values for the highway fuel economy test 
for HC, CO, and CO2 as specified in paragraph (b) of Sec. 
86.144 of this chapter. For tests of gasoline-fueled vehicles, measure 
and record the test fuel's properties as specified in paragraph (c) of 
this section.
    (2) Calculate the grams/mile values for the highway fuel economy 
test for HC, CO, and CO2 by dividing the mass values obtained 
in paragraph (b)(1) of this section, by the actual distance traveled, 
measured in miles, as specified in paragraph (h) of Sec. 86.135 of this 
chapter.
    (c) Gasoline test fuel properties shall be determined by analysis of 
a fuel sample taken from the fuel supply. A sample shall be taken after 
each addition of fresh fuel to the fuel supply. Additionally, the fuel 
shall be resampled once a month to account for any fuel property changes 
during storage. Less frequent resampling may be permitted if EPA 
concludes, on the basis of manufacturer-supplied data, that the 
properties of test fuel in the manufacturer's storage facility will 
remain stable for a period longer than one month. The fuel samples shall 
be analyzed to determine the following fuel properties:
    (1) Specific gravity per ASTM D 1298.
    (2) Carbon weight fraction per ASTM D 3343.
    (3) Net heating value (Btu/lb) per ASTM D 3338.
    (d) Calculate the city fuel economy and highway fuel economy from 
the grams/mile values for HC, CO, CO2 and, for test of 
gasoline-fueled vehicles, the test fuel's specific gravity, carbon 
weight fraction and net heating value. The emission values (obtained per 
paragraph (a) or (b) of this section, as applicable) used in each 
calculation of this section shall be rounded in accordance with Sec. 
86.084-26(a)(6)(iii). The CO2 values (obtained per paragraph 
(a) or

[[Page 900]]

(b) of this section, as applicable) used in each calculation of this 
section shall be rounded to the nearest gram/mile. The specific gravity 
and the carbon weight fraction (obtained per paragraph (c) of this 
section) shall be recorded using three places to the right of the 
decimal point. The net heating value (obtained per paragraph (c) of this 
section) shall be recorded to the nearest whole Btu/lb. These numbers 
shall be rounded in accordance with the ``Rounding Off Method'' 
specified in ASTM E 29-67.
    (e) For gasoline-fueled automobiles, the fuel economy in miles per 
gallon is to be calculated using the following equation:


mpg=(5174x10\4\xCWFxSG)/

 [((CWFxHC)+(0.429xCO))+(0.273xCO2))

 x((0.6xSGxNHV)+5471)]

Where:
HC=Grams/mile HC as obtained in paragraph (d) of this section.
CO=Grams/mile CO as obtained in paragraph (d) of this section.
CO2=Grams/mile CO2 as obtained in paragraph (d) of 
this section.
CWF=Carbon weight fraction of test fuel as obtained in paragraph (d) of 
this section.
NHV=Net heating value by mass of test fuel as obtained in paragraph (D) 
of this section.
SG=Specific gravity of test fuel as obtained in paragraph (d) of this 
section.

    Round the calculated result to the nearest 0.1 miles per gallon.
    (f) For diesel automobiles, calculate the fuel economy in miles per 
gallon of diesel fuel by dividing 2778 by the sum of three terms:
    (1) 0.866 multiplied by HC (in grams/miles as obtained in paragraph 
(d) of this section),
    (2) 0.429 multiplied by CO (in grams/mile as obtained in paragraph 
(d) of this section), and
    (3) 0.273 multiplied by CO2 (in grams/mile as obtained in 
paragraph (d) of this section).
    Round the quotient to the nearest 0.1 mile per gallon.

[51 FR 37851, Oct. 24, 1986]