[Dave Elliott]

Quote: Originally Posted by Razorlite (original)

Difference in RON makes absolutely no difference to the performance of the Mini Cooper S - also makes no difference to the 'cleanliness' of the fuel as that factor is completely down to the quality of the additives in the petrol.

BMW would never endorse a policy of dynamically mapping the car a few degrees/clicks closer to det just to gain a few BHP because of a higher RON level otherwise you risk of knock/pinking if a bad bit of fuel hit the engine.

Fact is, a car is either specifically mapped for higher RON values or is it isnt unless you are lucky to own a high end ECU such as pectel/motec etc that can be configured to dynamically change click values based on detected RON (RON is also only half the story).

This corresponds to what I have experienced with my 2002 MCS. I bought the car about 16 months ago and have always used BP Ultimate (98RON).

Recently my wife filled it up with Shell Premium (95RON) and I noticed a difference in the way the MCS drove. It was smoother (less "yoyo") and more responsive, especially from a standing start.

My MCS also has had the “cold start problem” and the 95RON seems to have made some improvement in this area too.

I'm now on my 3rd tank of Shell Premium (95RON) and I've noticed only a very slight decrease in fuel economy (530 instead of 550km from a tank).

I have a feeling that my MCS is factory tuned for 95RON and using any higher is a waste of money.

This observation could also partially account for the aftermarket re-maps gaining so much power.


Cheers,

Dave

[superunleaded]

I agree with the last poster. I have an Auto MCS and I have tried high octane (Shell Premium). The best way I can describe the change is that the car becomes hyperactive, jumping from standing start with much more frantic acceleration, rapidly spinning the engine and changing gears more frenetically. It becomes almost impossible to sqeeze on the throttle in a controlled manner. With standard unleaded the car becomes more civilised. It holds the gears longer. It is as if the car is designed for regular unleaded.

[Dave Elliott]

Quote: Originally Posted by superunleaded (original)

I agree with the last poster. I have an Auto MCS and I have tried high octane (Shell Premium). The best way I can describe the change is that the car becomes hyperactive, jumping from standing start with much more frantic acceleration, rapidly spinning the engine and changing gears more frenetically. It becomes almost impossible to sqeeze on the throttle in a controlled manner. With standard unleaded the car becomes more civilised. It holds the gears longer. It is as if the car is designed for regular unleaded.

Not sure where Superunleaded is from, so perhaps the Shell Premium he speaks of is of a higher octane rating than the 95RON in Australia.

Just to clarify my post: I have run my 2002 MCS for over a year on BP Ultimate (98RON) and just changed to Shell Premium (95RON).

Shell Premium (95RON) has made the MINI smoother and more responsive. Cold-start problem is not as evident and the yo-yo has all but gone.

Traffic-light starts used to be a real problem when running on 98RON. The car would sometimes lurch forward and then bog down. With 95RON there is no hesitation and the power can be fed in smoothly. It's certainly easier to drive, if not a bit faster.


Cheers,

Dave

[superunleaded]

I am in the UK and we have Shell V-Power (99 RON)

[caesar]

Quote: Originally Posted by superunleaded (original)

I am in the UK and we have Shell V-Power (99 RON)

I think you will find the MCS engine's ECU is setup depending on the country where it will be used because the petrol specifications vary. In the UK we have higher octane ratings than say the USA. So a fuel rating that gives better performance in the UK will not necessarily do the same for an MCS in the USA

[TheBigNewt]

No, in the UK they use a different numbering system for fuels than they do in the US. Here the highest number you can buy is 93 in eastern states, 91 in most western states. Same stuff as the UK, different numbering system, that's all. (I think someone explained it early in this thread).

[chris at woodman bmw]

I started using the good stuff a couple of weeks ago (v power) for the first couple of days on v power my MPG went down to 28-29 mpg,but a few days after the mpg went back to 34-35mpg,

[chris at woodman bmw]

I started using the good stuff again a couple of weeks ago (v power) for the first couple of days on v power my MPG went down to 28-29 mpg from 33-34 mpg,but a few days after the mpg went back to 34-35mpg, not sure why ,it could be the ECU sorting its self out but my car seemed to idle smoother and be more responsive