If you're going to get vapor lock running mogas, spring is probably the
time it'll happen. Oil companies formulate mogas for different seasons.
Winter mogas has a low vapor pressure which allows it to vaporize more easily
in lower temperatures. Summer blends have a higher vapor pressure to resist
vapor lock in warmer temperatures. The problem exists when using a winter
blend of mogas when temperatures have warmed up. If you're going to get
vapor lock, that's when it's most likely to happen.

It's not a problem in cars, since a typical gas station turns over its
stock one or more times a week. It can be a problem if you get your mogas
from an airport. It can take weeks or months to turnover a full load of fuel.


This was a problem with a friend of mine that runs an FBO in the southwest.
He used to have a self-serve mogas pump at his relatively small airport, and
it would take him a couple of months to sell a 2,000 gallon load of it.
Invariably, when the hot weather hit, he would get reports of vapor lock from
pilots who were buying his winter mogas. Eventually, he considered it too
much of a potential liability and shut down the mogas pump.

John Galban=====N4BQ (PA28-180)

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