I have seen a lot of differing opinions about what gas to get and from where. I am from the northeast and typically get 89 from Irving.

I have had issues where the car (2015 R60 S ALL4) would sputter when downshifting (automatic) from 6th to 5th on a hill climb to pass someone on the highway. The car would then have a rough searching idle for a day or 2. I don't have any other issues with performance or sputtering in any other circumstances (different gears, flat road, etc...). Further, a code was never thrown so the dealership couldn't do anything about it and blamed it on the gas.

I have read posts where people will sometimes use higher octane rated gas and/or gas from Shell (higher fuel cleaning additives?).

My gas cap and manual both state 89 as the type of gas to put in, but I am considering changing up my routine to make my car last as long as it can and to get the best value out of it.

I suspect that people will have strong opinions one way or the other, but am interested in hearing them.

 

I didn't think there were many owners who didn't use Premium fuel from a top shelf vendor in their MINI's after all of the threads on this site discussing this issue. I've used premium (91) since day 1 (usually from Shell, Esso or Petro Canada up here in Canuck land) and because the car has always run well, I've no plans to change.

 

Use only Top Tier fuels. Also, a can of BG-44K added at the pump every few thousand miles makes a noticeable difference.
Top Tier website: https://www.centerforqa.com/top-tier-gasoline/

 

Interesting, well hey at least the usual routine involved a gas provider that is listed on the top tier site. Now what about the octane rating? Do you just match what the manual state or do people run 91 or 93 part or all of the time?

I have used a fuel additive and I didn't really notice any difference. Part of me thinks that the downshift issue is due to an O2 sensor. Luckily I can work around the issue by not pushing the car to downshift to pass on a hill climb.

 

If top tier fuel is really a root cause (highly doubt it) then you could drain your fuel (or burn it up driving) and put a tank of top-tier 91 or 93 and go from there and see. Unless people are going to now say that you've damaged your fuel system by not using top-tier, etc.

 

My 2015 Countryman S All4 clearly says to use high octane/premium fuel only....I can't believe anyone would not use premium fuel in a turbocharged engine.

However, for what it's worth, we recently had a rental car while our car was in the body shop, and I put 87 octane in it...this was a Ford Focus...the fuel cap didn't say premium fuel only, and it wasn't turbocharged. Well, immediately after putting about $10 in of regular octane 87 it started running like crap! So, I asked my wife to look at the owner's manual in the glove box, and sure enough it said for better performance to use premium fuel as you may experience sputtering/missing with regular (or maybe it simply said you may have decreased performance, I don't remember the exact wording). Mind you, it did not specify premium anywhere but this statement in the manual. Go figure!

 

interesting ..... just sold my '14 FOCUS ST ... one of the performance models . . . turbo 4 cyl. The ST SUPPLEMENT to the owners manual mentions that regular is FINE but using 'high octane' MIGHT yield 2% more HP <under the most extreme conditions>. I ran regular for 4 years and the car ran great . . . as did my MINIs .... now my Mini on the other hand!!!!!! OMG, put less than 90 octane in that and OMG. It is a FAST test of independent gas stations CLAIMING to offer 'high octane, lead free" ...... Most cause my classic to kick, buck and run-on ...... Then I go back to a BRAND with 90+ and all is well . . .

I'll generally agree that octane++++ makes sense in a higher compression engine (turbo or super) .... but today's computer controlled systems compensate .........

my Mini ...... NO COMPUTERS

 

Yes always run the highest octane fuel available. My manual and inside of the fuel door booth have it printed to use premium only. That doesn’t mean too tier, it’s highest octane. You should see much better running after a couple of tanks to flush out the old completely. You should probably dump a bottle of bg44 or Techron fuel system cleaner when you fill up next also. I use Techron every 5 tanks or so. For my tune I actually run a mix with E85 just a tad, for a better octane rating for my tune.
You should be changing the oil every 5k miles too..... regardless of what the manual or on-board computer tell you. Your motor and turbo will thank you.
good luck