Page 633 - The Central Motor Vehicles Rules, 1989

ANNEXURE IV-G THE CENTRAL MOTOR VEHICLES RULES, 1989 605

(1) The values quoted in the specification are "true values". In establishment of their
limit values the terms of ISO 4259 "Petroleum products - Determination and application
of precision data in relation to methods of test" have been applied and in fixing a
minimum value, a minimum difference of 2R above zero has been taken into account;
in fixing a maximum and minimum value, the minimum difference is 4R (R =
reproducibility).
Notwithstanding this measure, which is necessary for statistical reasons, the
manufacturer of fuels should nevertheless aim at a zero value where the stipulated
maximum value is 2R and at the mean value in case of quotations of maximum and
minimum limits. Should it be necessary to clarify the question as to whether a fuel
meets the requirements of the specifications, the terms of ISO 4259 should be applied.
(2) The fuel may contain oxidation inhibitors and metal deactivators normally used to
stabilise refinery gasoline streams, but detergent/dispersive additives and solvent oils
must not be added.
(3) The actual sulphur content of the fuel used for the Type I test shall be reported.

Reference Fuel G23

Characteristics Units Basis Limits Test method
Minimum Maximum
Composition : % mole 92.5 91.5 93.5 ISO 6974
Methane % mole — —
Balance % mole — — 1 ISO 6974
[Inerts+C2/C2+] % mole 7.5 6.5 8.5 ISO 6974
N2
3(1)
Sulphur content mg/m — — 50 ISO 6326-5
(1) Value to be determined at standard conditions 293,2K (20˚C) and 101,3 kPa

Reference Fuel G25
Characteristics Units Basis Limits Test method

Minimum Maximum
Composition :
Methane % mole 86 84 88 ISO 6974
Balance
[Inerts+C2/C2+] % mole — — 1 ISO 6974
N2 % mole 14 12 16 ISO 6974
Sulphur content — — 50 ISO 6326-5

(1) Value to be determined at standard conditions 293,2K (20˚C) and 101,3 kPa
Note : G-20, G-23 and G-25 are three types of CNG fuels, out of which any two are
selected for testing of vehicles/engines to take care of the variation in the commercial
NG Fuel. The nomenclatures G-20, G-23 and G-25 are as used in EEC.