95 RON in an e92 M3

[Front bottom]

Hi, recently I've bought an e92 M3 which is very uneven on tickover from cold (hunts, then revs drop, then hunts again). I'm on a Facebook (yes, I know) group for these and others have had the same issue.

Some recommend you stick with V-power, and it will settle down (I use Tesco Momentum), but the nearest Shell garage is about 10 miles away, whilst others say the S65 engine was designed to run on 95RON.

Has anyone here heard this before?

[JMBMWM5]

I used safeway 97 in all my "M" cars, never had a problem, 95 ron is probably your problem, change too tesco 99 or sainsbury 97 and give it a good hard run, it will settle then IMO.

[Tony B2]

The S65 engine is optimised for 98 RON, but the adaptive ECU will allow it to run on 95 without damage - but with less power, and throttle response somewhat inhibited.

You will definitely not get the best from this engine on 95RON.

The cold start idle hunting problem is extremely common, has nothing to do with octane ratings and normally disappears after a few starts. In my opinion it is related to a change in ambient conditions since the last engine switch-off, with the engine taking a few moments to adapt to the new/current conditions (my experience is that it always seems to happen in Spring/Autumn, when the weather conditions are less stable).

And I always use 98RON or better.

So may say I am talking bks...

[Front bottom]

JMBMWM5 said:

I used safeway 97 in all my "M" cars, never had a problem, 95 ron is probably your problem, change too tesco 99 or sainsbury 97 and give it a good hard run, it will settle then IMO.

I use Tesco Momentum and always used it in my e46 M3 too without issue.

There is a lot of fuel snobbery with M cars though, with some owners looking down on supermarket fuel.

[Front bottom]

Tony B2 said:

The S65 engine is optimised for 98 RON, but the adaptive ECU will allow it to run on 95 without damage - but with less power, and throttle response somewhat inhibited.

You will definitely not get the best from this engine on 95RON.

The cold start idle hunting problem is extremely common, has nothing to do with octane ratings and normally disappears after a few starts. In my opinion it is related to a change in ambient conditions since the last engine switch-off, with the engine taking a few moments to adapt to the new/current conditions (my experience is that it always seems to happen in Spring/Autumn, when the weather conditions are less stable).

And I always use 98RON or better.

So may say I am talking bks...

One owner I spoke to on the Facebook page reckoned there was no detectable drop in performance when he used the 95.

[ndj]

http://forums.m3cutters.co.uk/showthread.php?t=550...

[Front bottom]

ndj said:

http://forums.m3cutters.co.uk/showthread.php?t=550...

Thanks.

The hunting thing seems quite widespread. Mine is an AUC, so I'm not overly worried, although I thought it was down to fuel. I didn't consider software updates.

[Max Maxasson]

Front bottom said:

Thanks.

The hunting thing seems quite widespread. Mine is an AUC, so I'm not overly worried, although I thought it was down to fuel. I didn't consider software updates.

You definitely want to be on later ECU software...from somewhere around mid- late 2012 or thereabouts.
And running 98 ron in a car optimised for this fuel will give the best performance.

[Front bottom]

Max Maxasson said:

Front bottom said:

Thanks.

The hunting thing seems quite widespread. Mine is an AUC, so I'm not overly worried, although I thought it was down to fuel. I didn't consider software updates.

You definitely want to be on later ECU software...from somewhere around mid- late 2012 or thereabouts.
And running 98 ron in a car optimised for this fuel will give the best performance.

Yeah, mine is a 2008 model. I could contact Sytner (who I bought it from) for a possible update I suppose.

Edited by Front bottom on Saturday 21st October 14:12

[Wills2]

Front bottom said:

Tony B2 said:

The S65 engine is optimised for 98 RON, but the adaptive ECU will allow it to run on 95 without damage - but with less power, and throttle response somewhat inhibited.

You will definitely not get the best from this engine on 95RON.

The cold start idle hunting problem is extremely common, has nothing to do with octane ratings and normally disappears after a few starts. In my opinion it is related to a change in ambient conditions since the last engine switch-off, with the engine taking a few moments to adapt to the new/current conditions (my experience is that it always seems to happen in Spring/Autumn, when the weather conditions are less stable).

And I always use 98RON or better.

So may say I am talking bks...

One owner I spoke to on the Facebook page reckoned there was no detectable drop in performance when he used the 95.

I found that the engine felt stronger, more urgent and crisper with higher octane fuel in my experience and BMW made the car optimised for that fuel grade.

[mike150]

The sticker inside my fuel cap says 95-98ron so I have to think BMW didn't put that there unless they where sure either octane was fine.

I have never tried 98Ron but maybe I will to see if there's a difference. It's quite hard to get where I live.

[Max Maxasson]

mike150 said:

The sticker inside my fuel cap says 95-98ron so I have to think BMW didn't put that there unless they where sure either octane was fine.
I have never tried 98Ron but maybe I will to see if there's a difference. It's quite hard to get where I live.

I think its more of a: 95 ron is ok if you must....the declared BHP is with the engine using 98ron.
If you switch to 98 ron you won't feel an immediate difference as the ECU will takes its own sweet time to recalibrate to the better fuel.
Conversely if you switch from always using 98 ron to 95 ron you can get the engine to noticeable pink when you drive off the forecourt./

[John Laverick]

I used both with no detectable difference (other than improved economy with 98).

Your idling issue is not being caused by the fuel RON rating, it should be happy on either.

[Tony B2]

I agree with your point about idle hunting being fuel independent, but not the general point.

Once adapted to the fuel the engine is much more responsive on 98RON

And bloody brilliant on 102, purchased next to the Nurburgring. I was easily able to get to the speed limiter (162mph) without even using full throttle, and acceleration felt like the car was 1 gear lower than it really was (6th felt like 5th, 5th felt like 4th etc)

[John Laverick]

Tony B2 said:

I agree with your point about idle hunting being fuel independent, but not the general point.

Once adapted to the fuel the engine is much more responsive on 98RON

And bloody brilliant on 102, purchased next to the Nurburgring. I was easily able to get to the speed limiter (162mph) without even using full throttle, and acceleration felt like the car was 1 gear lower than it really was (6th felt like 5th, 5th felt like 4th etc)

You can't disagree with me .... the fact is I noticed no difference in day-to-day driving .... your experience is obviously different which is fair enough.

[GroundEffect]

Tony B2 said:

I agree with your point about idle hunting being fuel independent, but not the general point.

Once adapted to the fuel the engine is much more responsive on 98RON

And bloody brilliant on 102, purchased next to the Nurburgring. I was easily able to get to the speed limiter (162mph) without even using full throttle, and acceleration felt like the car was 1 gear lower than it really was (6th felt like 5th, 5th felt like 4th etc)

All in your head.

[ant man]

The S65 produces 420hp with 98ron fuel. Evolve tested the difference of 95 vs 99ron (Shell Vpower) a few years ago and it is 10bhp.

[AW10]

I wonder what that translates to in real world use. Noticeable by mere mortals? Not to say that M drivers are mere mortals of course...

[John Laverick]

ant man said:

The S65 produces 420hp with 98ron fuel. Evolve tested the difference of 95 vs 99ron (Shell Vpower) a few years ago and it is 10bhp.

Which is why I didn't personally notice a 2% drop in power during day-to-day use.

[rassi]

I ran mine on a mix of 95 and 98, and must say I never noticed any change of performance or fuel economy regardless.