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I've noticed while reading through old posts that some people use 95 ron (normal unleaded) petrol in their S4s most of the time and every now and then put in a tank full of 98 ron to "have a play".
Correct me I'm wrong but if you normally use 95 and then all of a sudden put in a tank of 98 the ECU will not have time to alter things to get the benefit of the 98 (I've heard that it takes 2 or 3 tank fulls)
This means that they spend the extra money for nothing unless they keep using 98
The other thing I've heard is that if you use 98 regularly and then fill up with 95 the ECU will alter for the 95 straight away (typical!!)

Before anyone shouts .. I know that most will prob use 98 or higher anyway (I do) but it seems a shame for the people who use 95 to waste their money on the occasional tank of 98 (unless they reset their ECU)
Just my thoughts.

I've not used 95 since I was 17 and had a Nova SR

Always use super in mine, would only put 95 in if a) desperate or b) skint.

The ECU will quickly <beep> the timing if a lower grade fuel is used, the ECU will detect the detontation through the knock sensors, this is to protect the engine from damage as detontation increases engine temperatures and in severe cases melt pistons or valves.

Aldouk wrote:...if you normally use 95 and then all of a sudden put in a tank of 98 the ECU will not have time to alter things to get the benefit of the 98 (I've heard that it takes 2 or 3 tank fulls)
This means that they spend the extra money for nothing unless they keep using 98
The other thing I've heard is that if you use 98 regularly and then fill up with 95 the ECU will alter for the 95 straight away (typical!!)...

That's what I'd heard too, which (if true) would render super unleaded pretty pointless in terms of extra performance/mpg if you only use it occasionally.

It may have other benefits though such as better detergents or additives which might help to clean the innards of the system?

we have a BP here in MIlton Keynes selling 102 grade fuel, anyone ever given it a go?

lee_whitehead wrote:we have a BP here in MIlton Keynes selling 102 grade fuel, anyone ever given it a go?

Not heard of it found my way yet, still on the tesco99 stuff. WHEN they have it in stock tho! Seems pretty popular.

yeah, when I drove to Munich all the petrol stations in Germany have it, its called Racing Fuel over there !

Certainly helped me top 170mph vs. an S5

Do you need to get your car mapped specifically for that fuel? or do you need to run the 2-3 tank thing on it so the ECU adapts? The only thing that bugs me about it is the small availability of it nationwide