Corvair Forum

Question for olcorvairguy:

Do modern leaded fuels also have such a short shelf life?

I like to fill my tanks on selected cars in storage to prevent corrosion in the tank. I can still get 100+ octane leaded (Sunoco/VP) at most race tracks and will typically haul some home.

Thanks for the info.
Good discussion.

I am not sure of the Sunoco Racing fuels, but I will tell you that we have Shell Low Lead Aviation fuel at our facility and it has a octane rating of 105. it's not the fact of the Octane or the Lead content that determines the fuels shelf life, fuel just has a shelf life. If you leave gasoline in the open what happens is it evaporates it's Butyl and Ester properties and absorbs huge amounts of moisture, that's what leaves you that nasty stale smelling shellac crap in the bottom of old fuel tanks. My Statement of the 30 day shelf life is based on Ethanol blend fuels, the Ethanol in the gasoline sucks in huge amounts of moisture, and starts the Breakdown process four times faster. Most large chain Gas stations dont have problems with stale date fuels as they can turn their fuel stocks over as many as 20 times a month per storage tank.To your original question, the Aviation fuel at our facility gets filled once or twice a year depending on demand, and I take the moisture readings every month with no significant moisture retension( Summer or winter) so if you have access to a good qauility fuel then keep your tanks full, but I would not leave it in any longer than a year.


Regards Jim

My engine was rebuilt by a local racing engine company. I have tried ethanol free - (highest ethanol I could find locally) and high octane with ethanol. The car did not run as good with the ethanol free octane fuel. I think I may just be in an under served market that only has ethanol fuel and hard to find ethanol free high octane fuel. I have head the octane boosters don't do much to really boost the octane. Does anyone have some solid advice?

I have been driving Corvairs since the 1960's, and I have found that normally-aspirated, non turbocharged Corvairs are fairly tolerant of mid-grade and even Regular fuel. Carbon build-up in combustion chambers and tuning differences can have some impact. Higher ambient temperatures and a heavily loaded Corvair ─ particularly when driving up lengthy uphill grades ─ may cause pinging (detonation) and the need for higher octane fuel and/or adjusting the timing to retard it somewhat may surface under those driving conditions. The compression ratio is only 8.0:1 or 9.0:1 depending on your engine, but the somewhat higher normal operating temperatures of the air-cooled engine is certainly a concern and the driver must be alert for the sound of potentially destructive detonation (pinging) as driving conditions change. I have never used octane boosters and seldom use Premium fuel in a non-turbo Corvair.

Octane boost is the devil, only thing I ever got from that stuff is fouled plugs!