
Gasoline Air:Fuel Ratio

Stoichiometric Ratios of Various Fuels
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The stoichiometric or optimum air/fuel ratio for gasoline engines is 14.7:1 (14.7 parts oxygen to 1 part fuel). Stoichiometric means it is the chemically correct ratio of air:fuel by mass in which, theoretically, all of the oxygen and all of the fuel are consumed. This mixture is neither rich nor lean; at this ratio a gasoline engine produces both the greatest energy with the lowest harmful exhaust emissions.
Different Fuels have different stoichiometric ratios; for gasoline the optimum ratio is 14.7:1, for natural gas (which is almost pure methane) it is 17.2 :1. Other fuels such as diesel, ethanol or propane have their own stoichiometric ratios.
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