1985 3.2: What octane?

[911hillclimber]

I've had my (UK spec) 3.2 engine, now 140K miles old and never been apart since 1994 in my 1973T 911.
In all those years it has had Shell's finest petrol, in recent years 97 octane.

The nearest Shell station has changed over to ESSO, and they sell 99 octane.

The car seems to run quite a lot smoother in traffic or motorway and in this hot weather the engine runs about 2 degrees hotter in general.

Was the ROW 3.2 engines tuned to 99 octane/5 star fuels?

 

[sesame]

If I remember correctly the Owners Manual states the use of 4* petrol in the 3.2.
To expand further... That's why when lead was taken out of petrol, and ethanol was introduced, the rating dropped to between 3* and 4*. There is no knock sensor on the 3.2 engine to protect against pre-ignition damage (not always audible) to automatically temporarily retard the ignition like on later / modern engines.
3.2 owners couldn't physically retard the ignition as advised for daily drivers like sierras and cavaliers etc. of the time, so premium it is! Porsche now state more than 5% ethanol should not be used in classics, another reason to use the higher grade fuels.

 

[911hillclimber]

Thanks for the details. I have no handbook, the engine is a 3.2 in my 1973T 911.
Once ran a full tank through the car of 85 octane (before it was called E10) so maybe no ethanol, but it was noticably rough.

Some Shell 99 octane restored order again. Never run the engine on E10 but of course now E5 so some ethanol present even in ESSO now..

 

[marc_tt]

In 2002 I called Porsche Stuttgart about this for a relatives 70's 911 and they advised use any of the Super Unleaded high octane petrol from the major oil companies and avoid the regular unleaded. This would have been pre E10 fuels.

Have called Porsche Stuttgart several times over the years for technical advice and found them very helpful when I've phoned.

As an aside, my old Vespa was transformed with super unleaded and very happily ran with BP, Esso and Shell super unleaded

 

[911hillclimber]

I think all 2 strokes need high octane fuels though probably designed for low quality fuels originally.
I run my Honda lawn mower on 97 octane Shell.

Try to use Shell all the time, but E10 in my 987.2 Boxster, nice when ECU's adapt!