Actually, Avgas has a lower vapor pressure, so doesn't cool the carb as much during atomization. Thus it freezes less water out of the air and is less prone to cause carb ice when conditions are ripe for carb icing.
Avgas is also refined diffferently and does not have the varnishes and oils that are present in Mogas. Many aircraft sit for long periods of time between flights. Avgas won't break down and leave contaminants in the fuel system. It will also retain it's octane rating after long periods of storage. If you have ever cleaned parts with Avgas, you will also see that it leaves no smelly oily residue. Additionally, Avgas has guaranteed qualities. The down side, 100LL contains roughly 4 times the amount of lead that was in the old 80/87 red Avgas. More lead than necessary for some of the older engines and the lead is completely unnecessary for most of the auto engines. Jeff Scott On Mon, 18 Sep 2006 16:33:36 -0700 larry severson <lar...@socal.rr.com> writes: > > >Avgas is reckoned to be less prone to carb icing - not sure why > that > >would be. > > Less water in the gas! > > >The lead in avgas also helps reduces valve seat wear. > > > >Avgas is also stored under somewhat better conditions than your > average > >forecourt You are much less likely to buy a quarter a pint of rain > water > >water with your 10 gals of fuel. > > Also, for those with lawn mowers, remember the problems starting > after not running all winter. > With avgas, I have started an engine that has sat 4 years with the > gas remaining in the tank, Try that with mogas. >