Gasoline Octane for 1977 911S

[6cylboxer]

Looking the specifications for my 1977 911S, i found that the octane recommendation is 91 RON - I do not know the equivalent here in the USA

[Showdown]

87. Your 1977 911 will be totally happy with 87.

[Bill Douglas]

Yes it's a low compression engine (8.5:1 if I remember correctly) so it doesn't need the higher octane fuel.

[manbridge 74]

Counterpoint: When it’s over 100F and engine is well loaded consider highest octane. Many 77 cars did not come with an oil cooler leading to quite high temps..

[frosty2]

So does this mean a typical 2.4 would likely be ok with 87 octane rather that
running the higher more expensive octane fuel. Would it be the same for the
“T” or an “S” engine.
Sorry not meaning to hijack the thread just find it interesting.
Thanks
Mike

[Bill Verburg]

Just a data point but my '76 C3 w/ the same 8.5 cr though a 3.0 instead of a 2,7, ran fine on leaded regular but didn't when leaded disappeared, In the post leaded era I always had to use high test

[kent olsen]

With the high price of fuel I've been running my 72T with a 9.5:1 twin plug 3.0L on the mid grade. I feel if you don't push it the engine will be fine. Just my opinion.

[EC900]

91 RON is 87 Octane. My 77 2.7L runs fine with 87 octane. Higher octane gas will have better detergents but aftermarket additives added to every other tank of 87 will compensate for the +$1 more for 91 octane at the pump, plus additive treatment keeps the carbon in check and the gas fresh when in extended storage.