Fuel choice

I recently purcahsed my first 911, so bear with me if the following question seems a bit dumb.

I have been running my 911T (72 2.4 mechanical injection) on 93 octane rating fuel with no problems. Reading the owners manual I noticed it specifies the use of 96 octane rated fuel.

Will the use of 93 octane damage the engine in any way? Are there additives which may be of benefit? Is 96 octane available at any of the large chain gas stations? Anyone have a recommendations to make?

Many thanks,

356@topseven.com

Remember the higher the octane the higher the resistance to detonation therefore the slower the burn. The rule is to run to lowest octane you can get away with without pinging or rattling. I run regular in my 2.7RS motor at 8.5:1 compression, it works perfect. If I run super I notice a noticable drop in performance, all of this based on sea level pressure. Your car at 7.5:1 compression can run on lamp oil, you need to lowest octane you can find to speed up the burn in your low compression engine, high octane will do noting for you except cost you money and performance.

Also, the 96 octane specified in the owners manual is a different measure of octane than what is available at the pump in the US today. Go with 'regular'.

I recently repurchased a car I had previously owned some years earlier when it was a genuine 2.4S. I ran that on super and it was fine. It has since had the 2.7 pistons and barrells added and I tried running it on what is called Optimax out here in Aust. It ran like a dog, less powerful than I remembered and not what I had expected for a 2.7 rebuild.

After about three tank fulls the penny dropped and I tried a lower octance fuel (96).

Well guess what happened it goes heaps better. We also have a lead substitute petrol in our country now which is claimed to be 92 Octane so I tried that next.

The 911 flies on that which I guess only confirms what Schmidt was saying. I can't believe the difference in the car for the three fuels. I never realised the difference it coud make. It is much smoother certainly more powerful and feels awesome with the 92 Octane fuel.



Clyde Boyer

I think I worded my previous reply poorly. The 96 octane in the owner's manual is equivilant to something like 90 octane today. I have also experimented with different octanes in my 2.5L (8.1 comp. ratio) and found a significant improvement at 89 octane over 93+ octane "premium" fuels.

Thanks for your help, better go fill the car up...