yip - fine explanation MEGA XP.

One other thing to add. As MEGA XP notes the E10 gas can absorb much more water than conventional gas - and eventually this water saturated ethanol will "phase" separate from the gasoline. This will cause two distinct layers in your gas tank. This is where the issues arise. First - the octane number goes down and second your engine cannot handle burning the separated ethanol. (Polaris states not to burn greater than 15% ethanol). No snake oils on the market will prevent this separation; however, some will minimize the impact of this water laden ethanol (such at Marine Stabil). Just make sure are not adding additives such as HEET that are just adding MORE ethanol and will just make the issue worse. And as MEGA XP notes the ethanol is an EXCELLENT cleaner - so there is no need to use any carb or injector type cleaner if burning ethanol gas.

The shelf life of E10 gas is less than three months once it is mixed. For this reason it is not mixed at the refineries, rather the gas and ethanol are mixed at the distribution centers before trucking to your local gas station. If you buy from a station that regularly turns gas over you are probably getting "fresh" gas - but if you buy from a way out mom-and-pop store that doesn't turn their gas over you could get gas that has already separated in their tanks. Even worse is that now you could be pumping more of the separated ethanol/water and actually pump gas with ethanol concentration much higher than 10%. (some places in New York were tested at concentration >40% ethanol).

My regimen: I buy 91 octane gas for any equipment that I don't use up the gas in a matter of a couple months. I buy from a company that is regularly turning over gas. I treat with Marine Stabil.

Here is a list of precautions for using ethanol gas. If you want further info on E10 gas poke around the fuel-testers site. Lot's of info.