Gasoline

:Petrol (petroleum spirit) redirects here. For the seabird, see petrel, spelt with an 'e'.

Energy content

Gasoline contains about 45 megajoules per kilogram (MJ/kg)

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Volumetric energy density of some fuels compared to gasoline:

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A high octane fuel such as LPG has a lower energy content than lower octane gasoline, resulting in an overall lower power output at the regular compression ratio an engine ran at on gasoline. However, with an engine tuned to the use of LPG (ie. via higher compression ratios such as 12:1 instead of 8:1), this lower power output can be overcome. This is because higher-octane fuels allow for a higher compression ratio - this means less space in a cylinder on its combustion stroke, hence a higher cylinder temperature, less wasted hydrocarbons (therefore less pollution and wasted energy), and therefore higher power levels coupled with less pollution overall because of the greater efficiency.

Related Topics:
Tuned - Compression ratio

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Note that the main reason for the lower energy content (per litre) of LPG in comparison to gasoline is that is has a lower density. Energy content per kilogram is higher than for gasoline (higher hydrogen to carbon ratio). In lay terms, we burn mass, not volume!

Related Topics:
Density - Hydrogen - Carbon

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As an interesting side note different countries have some variation in what RON is standard for gasoline, or petrol. In the UK, ordinary premium unleaded petrol is always 95 RON whereas super unleaded is usually 97-98 RON. In the US, octane ratings in fuels can vary between 87 AKI (92 RON) for regular, through 90 (95) for mid-grade (European Premium), up to 93/94 for premium unleaded or E10 (Super in Europe)

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