What gas do pre-1974 LEADED gas cars run?

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I run AVGas (100LL) in my 1970 Mercury. With compression of 11.3:1, I get pinging if I try to use 93.
 
To get you by the abundance of sarcasm, just use regular unleaded and don't t lose any sleep over it. I have had many old British sports cars over the years and they did fine. There are additives out there if you feel it necessary.
 
I drove a 1972 Pontiac for years back in the 80's. Anything from GM was already designed to run on unleaded fuel by then. (hardened valve seats)
 
Rip van Winkle, is that you?
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I run Hapco lead substitute in my old cars.
 
Originally Posted by jhellwig
How is this still a question after 46 years?
Time certainly flies.
 
Need more info, year of vehicle, engine etc. Back in the day Amoco recommended 4oz. of top oil each fill up. MM will suffice. Also this topic has been discussed before on BITOG.
 
1972 and later models have the hardened valve seats iirc. Valve recession is real for earlier engined vehicles and a lead substitute or AVgas should be used. You could just run unleaded until you lose a valve and then remove the heads and have hardened exhaust seats installed.
 
Originally Posted by sloinker
... Valve recession is real for earlier engined vehicles ...
Yes, especially if the engine is operated above 3000 RPM, according to a study published in the SAE magazine a few years back.
 
I seen a video from Chrysler dated 1973 saying to use lead substitute every 4th tank of gas. I've used MMO every other tank in my 66 Dodge Polara 383 for the past 2 years so far with no issues. The commercial lead subs are a joke/scam to me. I bought a case of Gunk lead substitute and it is repackaged kerosene at a crazy price. MMO, trans fluid, kerosene, 2-cycle oil will do the job IMO.
 
Originally Posted by wowthisexists
Can't get leaded gas no more
so what do LEADED cars use for gas?

So what vehicle do you have exactly and what is the year it was built?
 
It's OK to mix 100LL Avgas with non ethanol gasoline. The blend's octane may actually be higher than the ratio's would indicate, due to the "lead response rating" of the non ethanol gasoline. A 50/50 blend more than matches the octane of yesterday's 100 octane fuels (which were really 95 octane when rated (R/M) /2 )

The very high octane ratings of the 1960's were "Research" octane numbers. Today's fuels (in the USA) are (R/M) /2 rated. Not really comparable.
 
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