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Old 07-08-2010, 01:24 AM
nolan_speed nolan_speed is offline
Motorized Bicycle Member
Join Date: May 2010
Location: Seattle, WA
Posts: 30
Default Re: What gas is best?

Ethanol is really bad news for two strokes. The worst case is in outboards where they're in the moist marine air and the ethanol absorbs all the moisture in the air and it really makes two strokes run like crap and corrode, especially when stored for longer periods.

The main problem is that you never really know what gas has ethanol and what doesn't until you test for it. Most gas pumps say that they contain up to 10% ethanol, but that doesn't mean that it actually has any in it. Fortunately it's easy enough to test for with a test tube or a Tupperware and you can google how to do it.

These engines only need regular low octane to run well, however, if premium is guaranteed to be ethanol free, go for it. Don't assume that premium is ethanol free however unless it is specifically stated so.

I also would disagree with Tad Bit Tipsy about air cooled engines liking lower octane fuel. Many of the air cooled aircraft engines are low compression and do run better on 80/87 octane (not 87/88, that isn't an avgas rating) and there will be increased carbon deposits and plug fouling with the 100LL. There are, however, some higher compression aircraft engines or turbocharged engines (continental TSIO 520 for example) that do require the high octane. It's more about the compression and less about the cooling method.
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