Could higher octane fuel cause rough running?

[CJ1]

Hi,

I’ve just this week picked a 2014 Mini Cooper S F56 with 64000 miles on the clock, Absolutely love the car. Yesterday morning I needed to refuel the car and thought I would treat it to Tesco’s finest Momentum seeing as it is a “performance car”.

Drove about 100 miles, the felt a bit more powerful under acceleration however whenever I came to a stop and allowed the car to idle I noticed a shudder/vibration coming into the cabin, so much so the seatbelt was rattling against the bulkhead. The engine is whisper quiet and sounds no different there’s just a lot more vibration!

Looking in the owners manual it recommends standard 95, and I reckon the previous owner always used 95 considering the amount of miles they were doing (ex PCP car).

Anyone had a similar issue?
Thanks

[stevieturbo]

No.

[TooMany2cvs]

Potentially, on full boost - simply because you might be getting more boost than on 95.

But not at idle, no.

[anonymous-user]

Not to the point it would make the cabin rattle! (more advanced ignition allowed by the higher octain fuel is a result of a faster burn rate, which does sound harsher as there is a more rapid rate of pressure increase (shorter 10-90 mass fraction burn time))

Check the engine mounts would be my suggestion!

[GregK2]

CJ1 said:

Looking in the owners manual it recommends standard 95

Recommends? or minimum it recommends?

[CJ1]

DELETED: Comment made by a member who's account has been deleted.

As soon as I put the AC on it runs smoothly (raised the idle slightly), do you think Mini would be able to adjust the Idle speed? It has a 1 year Warranty.

[TooMany2cvs]

CJ1 said:

As soon as I put the AC on it runs smoothly (raised the idle slightly), do you think Mini would be able to adjust the Idle speed?

The ECU sets the idle speed to what it should be.

If it's not idling smoothly at that speed, it's broken.