My '72 runs very well on 87. Unleaded is all I can get anymore. I put some Marvel Mystery Oil in every other tank or so for some top end lubricant that I feel is missing since the lead has been removed and the alcohol has been added. I also use MMO in my carbs in the winter (3in1 in the summer). MMO seems high in detergents and also tends to keep things fairly clean.

however if you want more performance, you can run AV-GAS that has the higher octane levels.

Higher octane does not provide increased performance if your car does not pre-detonate on lower octane. Higher octane means that the fuel/air mixture is harder to ignite.

I've put 335 miles on my newly rebuilt engine, (1980) head work, cam #13001-N3626, round tops (new sig?) and used 87 octane, no other "treatments", and have yet to hear it ping, and it has only been SHELL!!!

Bonzi Lon

I think Arne answered your question at Post #6. I'll only add that unless you want to retard your timing - I'd stick with super-unleaded.

FWIW,

Carl B.

Ive been running the 87 octane with timing set at 10 BTDC in my 71. Never had any pinging issues.

I run 87 in both the Z and the 810 with no problems but they're both EFI dish piston cars. Believe or not, I have to run premium in the old 320. Head work, fixed breaker plate, centrifugal advance only, Weber carb etc.

After running nothing but 93 since getting her on the road- I felt the need to mess with perfection and tried a couple of gallons of 89- and kept some octane-boost handy. Well, the pre-detonation was so intense that the exhaust pipe was banging into the wheel well- I have the "slipstream positioned" pipe tip coming out behind the LR tire. I immediately pulled over and added the booster. Later I filled up with 93 and added half a can of Seafoam to the gas tank to clean it out- and she ran like a champ again.

I will NEVER do that again. I believe that I might have blown the engine or at least a piston or two from excessive pre-detonation, according to several horror stories I've read around here.

All this from a numbers-matching 2/71 L-24 engine with a stock compression ratio of supposedly 9.0- I would have thought the reaction would not have been so violent. I wish Sunoco had their 94 around- that always gave me the best performance on all of my older cars. I used to have a Mercedes 6.9- which was a 1970's vintage 450SEL with a 7-liter racing engine and adjustable suspension, and it loved the 94 too.