Petrol

[Golich]

On the odd occasions I couldn't get Optimax I honestly can't say I noticed any significant difference running my previous S4 (chipped) But I did anyway out of mechanical sympathy.

Any opinions on Q8's 98 ron?

[DrB]

I think Optimax does make a difference in performance. However the main differnce I see is in the miles I get out a tank. I usually get 30 miles extra while using optimax. Therfore normally over 300miles pertank. (mixed driving)

[Golich]

I definitely did get anymore miles. [img]images/graemlins/frown.gif[/img]

[runrowsam]

I normally run premium 95RON because I'm a povvy student and can't afford to run a 25mpg BMW on that, let alone 98RON! Besides, it's not exactly a performance beast. The old Mini I had though, that was a different story. A friend of mine was convinced Optimax was the dog's, and talked me into filling up from virtually dry with it. It made quite a difference. Power was up slightly, particularly at higher revs, but the throttle response was a lot more crisp. I also had a few more pops and bangs, not to mention the occasional flame out the exhaust [img]images/graemlins/crazy.gif[/img] Cam timing was slightly off, but I wasn't complaining! That engine was heavily tuned though, being the 1275cc A series running 95hp, which is good going by anyone's standards! But I'm guessing turbocharged engines will benefit more from higher octane levels.

Rock on
Sam [img]images/graemlins/thumbs.gif[/img]

[Brooner]

yes i can't see a diferance in miles per tank and i regularly use other super unleaded petrols and don't realy see a difrance in power between the diferant brands [img]images/graemlins/hatthing.gif[/img]

[Nige_RS4]

once ran the tank completely dry, then filled up with Superplus, but to me there seemed absolutely no difference, though my car is stock; modified cars may benefit perhaps? I know when I was running my Cossies a few years ago my mechanic insisted I stick to Super, as they were all severely modified.

It's been said before, but worth repeating for those that have missed the point, the S4 (and RS4) engine management will adjust to the quality of the fuel, but (and it's a big but) it will take some time to do this - AFAIK it can take upto 3 tankfulls to advance to the optimum settings, therefore you are unlikely to notice a big difference straight away.

this thread has some more info on how the ECU will advance/<beep> due to varying grade fuels.

Nige [img]images/graemlins/thumbs.gif[/img]

[Golich]

Your right Nige I've read that and should have known better. HHhmm but that's got me thinking...from day one of owning my car (second hand S4) I always put 97 or 98 in. So running with the theory that the timing has been advanced. Then in theory by introducing the lower octane fuel I should have one way or another noticed a reduction in the performance or knocking. Strictly speaking I would only get knocking if the knock sensors weren't working!

So it still begs the question just how noticeable is the diffrence between the 95 to 98 Ron fuels. The only time I can truthfuly say I've noticed a significant difference in performance is when the conditions are cool and damp, exactly what I would expect from any car turbo or NA [img]images/graemlins/crazy.gif[/img]

I try not to think too much about this and convince myself that the higher ocatne feul is better for the car and if it has detergents etc well that's all a bonus. [img]images/graemlins/tongue.gif[/img]