Discussion
I agree with Dr G, performance cars like that are tuned for 98 ron from the factory, all my beemers were and s4, I put nothing less than 99 ron in my cars. Even though its more expensive you restore the factory economy figures with it and about 20hp more too than 95 ron. You need to run on fumes then brim it a couple of times to make sure you clear out the crap fuel,
Edited by Andy70 on Tuesday 12th October 19:33
Mr Dendrite said:
I run my B9 RS4 on Tesco 99 momentum. For the sake of a couple of quid a tank why not. Let’s face it if you want fuel economy and are going to worry about the cost of petrol don’t buy a 450bhp estate car that does around 30mpg at best in the first place. 
Thats not a problem I have just ordered one up for next year and forgot to ask about which fuel. All ready looking at a stage onefor the car from Lichfield if anybody wishers to comment. Sold my GT3 which had 500 brake but lower torque figure.
Terminator X said:
Imho stick Super in any "performance" car.
TX.
Makes zero difference in many cases; moreso now everything is DI.TX.
If ECU is set to time/advance/boost/fuel a certain way on 95 and that fuel allows it to run those settings adding more octane will do nothing. DI means the detergent benefits are moot too.
If however the ECU is calibrated to do the same on 98 then using 95 will result in said ECU backing things off to avoid (or on the detection of) knock.
Dr G said:
Terminator X said:
Imho stick Super in any "performance" car.
TX.
Makes zero difference in many cases; moreso now everything is DI.TX.
If ECU is set to time/advance/boost/fuel a certain way on 95 and that fuel allows it to run those settings adding more octane will do nothing. DI means the detergent benefits are moot too.
If however the ECU is calibrated to do the same on 98 then using 95 will result in said ECU backing things off to avoid (or on the detection of) knock.
I have always used Super for the RS3, RS4, M5 and now M2.
TX.
Brand dependent there will be a detergent package, that if used on a direct injection engine means about nothing as the fuel is only ever in the combustion chamber, not the ports or inlet manifold. A port injection engine can take advantage of this.
The RON number indicates nothing more than a fuel's resistance to knock, and if it doesn't knock on 95 RON there's no advantage in feeding it anything different.
It isn't that adding more "octane" will make an engine run better, or more efficiently, it's that giving it insufficient octane will make the ECU run the engine in a compromised manner (hurting power, fuel economy, emissions etc.).
The RON number indicates nothing more than a fuel's resistance to knock, and if it doesn't knock on 95 RON there's no advantage in feeding it anything different.
It isn't that adding more "octane" will make an engine run better, or more efficiently, it's that giving it insufficient octane will make the ECU run the engine in a compromised manner (hurting power, fuel economy, emissions etc.).
Terminator X said:
Isn't the 99 ron stuff "better" fuel? Even if not afaik max performance requires Super surely vs the regular stuff?
I have always used Super for the RS3, RS4, M5 and now M2.
TX.
All of those cars you have had are designed from the factory to take minimum of 98ron, (it will say inside the filler cap flap. performance and economy is compromised if you use 95. I've always used 99 in all my cars, but that is purely because they are meant to have it. Every time I've bought cars over the years where the previous owner has used 95, I've noticed the difference after a few tanks of 99 I have always used Super for the RS3, RS4, M5 and now M2.
TX.
Just as another example, the V6T supercharged engine used in recent generations of S4/5 is designed to run on 95 and provide its maximum performance, and as Dr G says it makes no difference if you run it on 99. From memory the sticker on my fuel flap is very similar to above but quotes a minimum of 91 RON with recommendation for 95.
My old S8 (2002) on the other hand had the same recommendation as posted in the picture earlier, and you could notice a difference running it on 99 in terms of initial pick up and mid-range urge compared to 95.
Note that with remapping it depends what the tuner does to the map as to whether it will be setup for a higher RON or not.
My old S8 (2002) on the other hand had the same recommendation as posted in the picture earlier, and you could notice a difference running it on 99 in terms of initial pick up and mid-range urge compared to 95.
Note that with remapping it depends what the tuner does to the map as to whether it will be setup for a higher RON or not.
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