95 RON in an e92 M3

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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?

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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.

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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.

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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.

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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

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I think my post has become a little misunderstood. I was quoting someone from another forum (albeit Facebook) saying that the s65 was designed to run on 95RON. I was just wondering if anyone else had heard this.

I also mentioned fuel snobbery when it comes to M cars. There is some of that displayed in this thread.

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XMT said:

95 Ron is your issue.
Baffles me when people say they cant tell the difference.

V power all the way, even the BP ultimate is crap.

Tick over is the tell tale sign if your car likes it or not. Even in my N55 335i it hated anything but V power.

Some people say Shell V-power makes things worse, or it only appears when they use it. Others swear by the Esso 98RON stuff.

Me? I use Tesco Momentum. Mine has just come back from Sytner after having a throttle actuator replaced and I mentioned the cold start 'hunting' thing to them. They said it's normal, as did someone else I spoke to who has worked on many e92 M3s.

It's all part of the 'cold start cycle' apparently, which can be mapped out, which many owners do I suppose. That would explain why a lot of cars don't do it with present owners.