Quote:
Originally Posted by 40 Deluxe
GPierce, Just curious: Does the auto fuel contain ethanol? (I would think not.) And how high can you fly before "vapor lock" becomes a problem?
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I’ve flown to 13,000’ on ethanol free fuel but I won’t fly with ethanol adulterated fuel
The FAA does not allow certified aircraft to use fuel adulterated with ethanol.
When I use auto fuel in my airplane it is ethanol free.
Home built aircraft, of which there are thousands flying do use ethanol adulterated fuel. The higher you go the colder it gets so vapor lock isn’t usually a problem. We drive carburetor cars up to 14,000’..
Avgas vapor pressure remains constant at a 6.5-psi level regardless of the time of year or area of the country it is used. Autogas vapor pressure is often changed in some parts of the country from a high of 15 psi to a low of 7 psi. For that reason I wouldn’t use it but many do without apparent problems. 87 octane fuel is only used in aircraft engines up to 7.5:1 compression ratio. Some higher compression engines can use 91 octane ethanol free fuel, mine included but it’s hard to find. Avgas is only available at 100 octane.