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the first spec to look for is the compression ratio of an engine.

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compression ratio:

                                 there are 4 strokes in a 4stroke engine.

                                 1: intake.

                                 2: compression

                                 3: power.

                                 4: exchaust.

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after the fuel and air mixture is fed into the cylinder. it is compressed before the spark ignites it.

compressing it brings the air and fuel molecules close together and raises its temperature for an efficient burn.

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compression ratio is written as 10:1 or 9.5:1. the ratio sign ": " determines the compression ratio between the 2 values.

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fuels are rated in octane and ron . and the higher the octane the better it resists the combustion.

but why do we need to resist combustion when we are trying to combust the fuel mixture.

the answer is when we are trying to compress the air-fuel mixture it raises its temperature if the fuel is not the right octane range. then due to compression, the fuel will reach the temperature where it ignites without the spark. that causes knock and that damages the engine.

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and if you put high octane fuel into a low compression engine. then because the high octane. the fuel resists combustion. that results unburn fuel and exhaust gases that choke the catalytic converter foul spark plug and reduce power.

when the engine is operating we want combustion to occur at the right time and the right octane fuel helps to achieve that.

so the right type of fuel is required for proper combustion. here is the list of recommended octane ratings related to the compression ratio of an engine.

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Note: octane rating does not denotes the power that fuel can make.