Dear all hope this finds you well.. I was wondering what type of fuel would be best? Octane? Would 95 or 91 be better? Any ideas?

 

The best fuel for the map in the existing ECU is the fuel octane on the sticker in the cap. "More is better" is only applicable if you're tuning to take advantage of it.

What is your year and part of the world?

 

Read your owners manual if you have one. It lists it there.

It also lists it on a sticker behind the fuel door like here in post 2 :https://rennlist.com/forums/928-foru...available.html

 

Hi... Thanks a lot for your help..
I am currently in Saudi Arabia... The car year model is 1988..

 

Assuming we are talking about 95 RON that is what you should be running.

The first thing you need to be aware of is the fuel knock rating system used which unless something has changed since I last worked in KSA, is the same as the rest of the Gulf and is based on RON which generates numbers about 5 points greater than the US system [that uses the AKI rating system].

The S4 runs OK on RON 95 but has a tendency to knock on some cylinders [6 & 2 as I recall] at higher rpm's causing the engine management system to retard the ignition slightly on those cylinders but the driver is not aware of what is going on. I suspect this in part is caused by uneven air flow in the individual runners but may also in part be induced by chronic oil lifting as typically seen in these motors.

In Oman in years gone by we typically could only get 95 RON fuel as blended in the local refinery [I used to be the chief engineer there]. What some of us in the local Porsche club noticed was that when we went up to Dubai and filled with their Super 98 the cars fitted with anti knock control systems appeared to run a little bit better. We put this down to the engine not pulling the timing. Nowadays we have 98 RON available here at a cost premium. However as a user of ST2 I have yet to get around to optimising the ignition maps to get any benefit from using it shiuld I choose to do so..

 

Thanks a lot very informative... So I guess would be best ton use the available 95 and no 91 by all means? Higher octane would be best? Should I use octane boosters additives?

 

Just run the 95 RON- no need for octane boosters that generally speaking do little to nothing other than empty your wallet a bit more

 

I am in NJ USA, put 120K miles on mine and for 90% of the time used "mid-range" fuel. Most of that being highway driving.

Not saying that's good or bad, but over 25 years I have not seen any issues.

 

Thanks for sharing

 

Don´t do this with an early high compression S car.

 

Don't do what?

 

Go cheap on fuel octane to save $2.

 

Use 95 in Saudi and try to get it at one of the newer stations (Aramco) or a reputable one like the Idrees, Mobil, SASCO, etc. Avoid old and run down stations.

 

Will do... Thanks

 

Out here, in Kalifornia, the price difference between 89 and 91 is $.20 a gallon.
When the overall price is almost $5.00 per gallon, $.20 more isn't likely to cause anyone who owns a 928 to go without food.