In my area of the country it is now impossible to puy gasoline at any convenient store or gasoline station that does not have 10% ethanol blended in (E10), and it doesn't matter what grade (Regular or Premium). It is easy to test you fuel for ethanol content. Get a 20oz or similar empty soda bottle and mark a line about 2 inches from the bottom. Fill the bottle with water up to the line, then fill the rest of the bottle with the fuel you want to test. Put on the cap and shake the bottle then set it down and let the liquids settle. If the water level has risen above the line you marked - there is ethanol in the fuel. If the water line settles back to the mark you made then there is no ethanol in the fuel.
E85 is 85% ethanol and only 15% gasoline and I am pretty sure you will not want to attempt to run that in your saw or any power equipment with a carb.....it just won't work.
Gasoline blended with ethanol does cause problems in older equipment that was built prior to the onset of ethanol in our fuel. The ethanol does absorb moisture and can cause steel fuel tanks to rust and aluminum carbs to corrode. The ethanol also dissolves rubber fuel lines, gaskets and diaphragms.
In order to solve the ethanol related problems I have been able to buy 87 Octane gasoline from a bulk distributor that delivers fuels to farmers for use in the tanks on their farms. The distributor sells them fuel without the ethanol as it stores better in their above ground tanks and runs better in their old tractors. It works just fine in my equipment and the only drawback is I have to buy 100 gallons at a time - it stores just fine in 55 gallon drums with Sta-Bil added.
My experiments with 100LL Avgas proved to be OK....but it is a bit of a hassle to buy and you have to adjust the mixture on your saws to use Avgas as it runs a little richer than normal gasoline. I also don't believe the saws idle as well on it. Avgas however stores for years and does not leave any gum or residue when it evaporates.
I have no experience with the new fuel treatments for ethanol. I know that boat owners have had problems with the ethanol dissolving fiberglass fuel tanks and Sta-Bil has a Marine Formula that claims it solves the problems.
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