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This SAE Recommended Practice summarizes the composition of modern automotive gasolines, the significance of their physical and chemical characteristics, and the pertinent test methods for defining or evaluating these properties.

This SAE Recommended Practice summarizes the composition of modern automotive gasolines, the significance of their physical and chemical characteristics, and the pertinent test methods for defining or evaluating these properties.

Compressed Natural Gas (CNG) is a practical automotive fuel, with advantages and disadvantages when compared to gasoline. Large quantities of natural gas are available in North America. It has a higher octane number rating, produces low exhaust emissions, no evaporative emissions and can cost less on an equivalent energy basis than other fuels. Natural gas is normally compressed from 20 684 to 24 821 kPa (3000 to 3600 psig) to increase its energy density thereby reducing its on-board vehicle storage volume for a given range and payload. CNG can also be made from liquefied natural gas by elevating its pressure and vaporizing it to a gas. Once converted it is referred to LCNG.

The mass of air required to burn a unit mass of fuel with no excess of oxygen or fuel left over is known as the stoichiometric air-fuel ratio. This ratio varies appreciably over the wide range of fuels—gasolines, diesel fuels, and alternative fuels—that might be considered for use in automotive engines. Although performance of engines operating on different fuels may be compared at the same air-fuel ratio or same fuel-air ratio, it is more appropriate to compare operation at the same equivalence ratio, for which a knowledge of stoichiometric air-fuel ratio is a prerequisite. This SAE Recommended Practice summarizes the computation of stoichiometric air-fuel ratios from a knowledge of a composition of air and the elemental composition of the fuel without a need for any information on the molecular weight of the fuel.

The mass of air required to burn a unit mass of fuel with no excess of oxygen or fuel left over is known as the stoichiometric air-fuel ratio. This ratio varies appreciably over the wide range of fuels—gasolines, diesel fuels, and alternative fuels—that might be considered for use in automotive engines. Although performance of engines operating on different fuels may be compared at the same air-fuel ratio or same fuel-air ratio, it is more appropriate to compare operation at the same equivalence ratio, for which a knowledge of stoichiometric air-fuel ratio is a prerequisite. This SAE Recommended Practice summarizes the computation of stoichiometric air-fuel ratios from a knowledge of a composition of air and the elemental composition of the fuel without a need for any information on the molecular weight of the fuel.

Compressed Natural Gas (CNG) is a practical automotive fuel, with advantages and disadvantages when compared to gasoline. Large quantities of natural gas are available in North America. It has a higher octane number rating, produces low exhaust emissions, no evaporative emissions and can cost less on an equivalent energy basis than other fuels. Natural gas is normally compressed from 20 684 to 24 821 kPa (3000 to 3600 psig) to increase its energy density thereby reducing its on-board vehicle storage volume for a given range and payload. CNG can also be made from liquefied natural gas by elevating its pressure and vaporizing it to a gas. Once converted it is referred to LCNG.

The mass of air required to burn a unit mass of fuel with no excess of oxygen or fuel left over is known as the stoichiometric air-fuel ratio. This ratio varies appreciably over the wide range of fuels—gasolines, diesel fuels, and alternative fuels—that might be considered for use in automotive engines. Although performance of engines operating on different fuels may be compared at the same air-fuel ratio or same fuel-air ratio, it is more appropriate to compare operation at the same equivalence ratio, for which a knowledge of stoichiometric air-fuel ratio is a prerequisite. This SAE Recommended Practice summarizes the computation of stoichiometric air-fuel ratios from a knowledge of a composition of air and the elemental composition of the fuel without a need for any information on the molecular weight of the fuel.