That really pisses me off!!! You pay MSRP or close to it and they can't even put the proper grade gas in it!! I would demand another tank of gas! If they won't do that, give them bad marks on the MINI survey and report them to MINI USA,

 

Quick update. I've now covered around 900 miles and I'm on my fourth tank of gas. The octane rating should be back up to 93 and I'm using Mobil premium gas. There has been a significant improvement in performance (over the dealer's initial 87 octane fill-up) but I'm still not convinced the car's performing as it should.

I drove my wife's MCS this morning and it still feels noticeably more responsive than my JCW in all gears up to 4500 RPM with no flat spots....it feels eager to pull with slight throttle inputs; mine feels "flat" with no real get-up-and-go. I'm taking it in for an oil/filter change soon, so I'll have them check it out

 

Ask them to reset your ecu, and then drive it aggressively for the first hundred or so miles. The combo of cheapo dealer regular with the 'learning' ecu might have conspired to rob you of proper performance.

You should also write a letter to MINIUSA and the dealer prez about their gas policy - they have NO business dropping cheap crap (sorry) gas in your JCW.

 

I waited until I was close to the 1250 break-in period and then I started to drive it much more aggressively (almost to the point where I was driving around in one gear lower than necessary and always at, or above, 4000 RPM).....wow, what a difference. I guess the ECU is VERY adaptive. So, the moral of this story is; (a) always use the highest octane gas you can get and (b) if you drive reservedly the ECU will learn your style and reward you with great mpg but mediocre performance

In fact, my mpg has only dropped slightly with the more aggressive driving style; I'm now getting around 26 mpg (no stop-go city driving) and a car that finally hauls ***.