if you really want to get indepth on octane, read this: octane info detailed

 

So gasheads what works best in a water cooled 800 w/ efi,? The head mechanic at polaris dealer told me to run the lowest grade 87, said higher octane in these caused overheating. any ideas what is best?

 

Well we have beat this topic to death but I will post something I wrote in a snowmobile forum …………..I hope it answers your?

Well I will try to give you a short version of this :
premium gas was and is designed to protect your engine against detonation. and it does this because of the chemical makeup of long branch tightly bonded molecules. Where regular gas has a molecular structure that has less of a bond.
The chemical composition of the fuel determines how fast the fuel will burn and if it will work well with high compression or temperatures.
fuels with weak molecular structures [regular] will break down more quickly or burn spontaneously [detonation] at lower temperatures.
Fuels with tight molecular structures [ premium] burn more slowly and take more pressure and heat to fully break down and burn.
therefore putting premium fuel in a engine not designed for high octane fuel [I e not having high compression or spark advance ] will not be able to break down the chemical bonds. And will not completely burn the fuel charge therefore produce less power.
So you see next time your at the pump buying that 115 octane racing fuel for your sled that costs five dollars a gallon. you may want to reconsider. And by the way no fuel can be over 100 octane ! It's a percentage
Run the type of fuel your manufacturer recommends !!!!!