Ask The Editors: Does My ATV Need High Octane Gas?
We get this question a lot and it’s important to understand that octane is a rating of gasoline’s ability to resist pre-ignition or detonation. What is pre-ignition? It’s when your fuel ignites in the cylinder before it should. When this happens it is felt as engine knock or (in the case of our smaller single-cylinder ATV engines) pinging.
Under normal operating conditions, the fuel-air charge is meant to be ignited by the spark plug only, and at a precise point in the piston’s stroke. Knock occurs when the peak of the combustion process no longer occurs at the optimum moment for the four-stroke cycle. It happens earlier and the shock wave creates the characteristic metallic “pinging” sound, and cylinder pressure increases dramatically. Effects of engine knocking can range from an inconsequential annoyance to completely destructive to the top-end of your engine.
So again, octane rating is not a performance booster in and of itself, it is the measurement of the fuel’s ability to resist pre-ignition.
The reason modified engines often call for higher octane fuel is that the cylinder compression ratio is increased in this engines and hence the chance of pre-ignition occurring much greater.
Stock ATV engines are designed to run on pump gas and hence 87-octane should be sufficient in most cases. A lot of riders mistakenly believe that expensive high octane race fuel is providing their stock ATV engines with some sort of performance advantage. In actuality, fuel that contains more oxygen would provide a slight gain in horsepower if you are determined to spend money on expensive race fuels but for most engines, pump gas is good enough.