Supreme Gasoline

[kcoke]

Should I be running Supreme Gasoline or high octance gas in my 1971 240z? I just rebuilt the engine and was wondering what kind of gas I should put in it?

[MikeW]

High octane is only required if the compression ratio is high enough that the engine would pre-detonate (ping) otherwise. For a stock engine regular should be fine.

[kcoke]

My engine does "ping" in third gear....so I prob should use a higher octane gas?

[Arne]

My stock '71 needs premium, and the owner's manual specifies premium. You might get away with less octane if you have a later cylinder head, or a hot cam installed. But for a stock '71 L24, I'd recommend premium.

[MikeW]

At what RPM does it ping in 3rd?

Since Arne's engine is different than mine I suppose you should consult the factory service manual for your particular model. For mine, 1972 L24 with twin SUs and an 8.8:1 compression ratio the FSM specifies "more than 95" for octane. Where I live I can only buy 87, 91, or 93. It also specifies with emission control to use "91 (low lead)". I mostly use 87 and never notice pinging.

[ChrisA]

How's the timing? What dizzy are you running?

Might not be fuel related. Some cars will ping if the timing is off even with higher octane fuel.

Chris A.

[ChrisA]

Here's some interesting reading on knocking and pinging. List at the bottom of the article with many things that could cause pre-ignition.

http://www.omegamotors.com/enjoy/gasoline/gasoline_07.html

Chris A.

[kcoke]

Timing is good.....just checked it. Not quite sure of the RPM in third gear. I just remeber that right when i shift into third (at a lower RPM) it Pings. Im going to try and put a octane booster in the tank now because i have the low level octane in it now and next time I am going to get supreme gas. Hopefully it will get rid of the pingen.