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Choice of Gas


Well-known member
May 17, 2002
Toronto, Canada
1973 Red Coupe
Ok, this could be the dumbest question ever asked on this forum!

If a 1974 is th elast year of leaded gas, and I'm driving a 1973 which is leaded as well....why is it ok to put 91 and higher octane super unleaded in the tank?

Would performance be enhanced if I used a different gas? SHould I be adding a leaded additive?

Thanks gang for any advice.



Well-known member
Oct 14, 2001
Wasilla, Alaska, U.S.A.
'77 L-82, black on black. Full mod 406 small block
from what i have always heard,
the higher octane rating super unleaded allows for a smoother more "stable" or well controlled burn. it also burns cooler than lower octane fuels. when switching over to unleaded, it is a good idea to change the valve seats to more hardened ones. the lower octane unleaded has a tendancy to detonate and trash valve seats, not to mention burn hotter. lead is a good fuel stabillizer, and adding lead will only help your motor. lead actually lubes the valve stems and upper cylinder bore, not much but a little. or you can go with good fuel for a few cents more and not worry about the cost of lead additives. your valve seats should handle the super unleaded just fine.


I hear the same thing when I was looking for better gas to use with my motor (10.5:1 comp) and I ended up using 5 gallons of VP Racing Fuel C12 with every tank and my motor is much happier now. Another thing I heard when talking to the local hot rod types is that using additives like octane boost wasn't a good thing for long term use as there will be a build up of deposits from the additives. I don't know all that to be true, just passing on what I heard.

I don't know how it is where you live but we have a gas station in town that supplies 100-110 octane leaded fuel still, they will make you put it into a container but it's still available...although not cheap. Talk to the local racers or speed shop, they should know where to get some. My local speed shop sells it by the gallon too.


I'm afraid these guys are addressing extreme situations...

The fact of the matter is that your '73 will run fine on unleaded gas. The manufacturers had already adapted their engines to run on unleaded by that time. The only change in '74 is that Vettes got catalytic converters, which REQUIRE the use of unleaded fuel -- lead will clog the cats.

So go ahead and keep using good ol' Petro-Can super unleaded (and don't waste your money on lead additive).


In my area you can get CAM 2 gas form select Sunoco stations. Its $5 a gallon and 110 octane. Ocasionally I mix it about 1/3 to 2/3 rd 94 octane and my car loves it. It definitly make a very noticable diffrence. I have yet to try a tank of it straight just becuase it so damn pricey.

For the most part I just run the Sunoco 94 and the car runns fine on that, but with 10 : 1 compression it definitly apreachiates the good stuff.

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