So I finally got around to inputting all of my gas station receipts since November. Since I only need to fill up about once a month, I only had 4 receipts. Anyway, I noticed that my two most recent receipts showed that I had purchased "regular unleaded." I know that technically my MC can take regular unleaded but I feel that it runs better when I use premium so that is what I almost always put in it plus our weather in Boston has been horrendous, at least by my standards(4 degrees?!). For the previous two fill-ups I've gone to a full service station and apparently the guys filling my car up have ignored my request for premium both times. I'm from Texas. Full service stations have gone the way of the dodo bird so this was my first time since the age of 5ish that I've actually been to a full service station.

I had noticed since January that my MC was more sluggish than normal and that my mileage was down a bit (I'm averaging 26.5 mpg) so I had checked my oil and tire pressure, both of which are good. Is there anything else that I should check or is this normal mileage for Northeast winters? I definitely will be filling my car up myself from now on regardless of what the weather is doing.

 

I was getting 34 on premium. Then in a mood of frugality, I switched to regular. When the SEL light came on and my mileage dropped to 30 I decided to go back to being extravagant and stick with the good stuff. I've reset the code, now I'm hoping it doesn't come back. It's kind of like being scolded by the little guy, Will

 

If you wish to take the time to peruse NAM for all the comments posted over the past several years about MINIs and fuel you will find that taking shortcuts, accidentally pumping the wrong fuel, letting someone else who doesn't understand or just plain poor judgment all boils down to one fact: MINIs are designed to run on high performace fuel and will cough up their guts if fed otherwise. The worst and most expensive uh-oh is a burned out knock sensor accompanied by the dreaded CEL. There's an old chestnut that goes: "Penny wise and pound foolish" for those that choose to ignore the directive. In the case of the OP's situation, a lot firmer grasp upon the nape of the attendant's neck might be in order. You expect to get exactly what you request from those people and let them know what they [should] be liable for if they fail. Hope you can get them straightened out. I would be peeved in the extreme.

http://www.toptiergas.com/retailers.html

 

The last two posters were gen1 car owners...those cars have a different motor, and REQUIRES premium fuel (91)....many folks have tried less...sometimes with issues.
As a gen2 owner, with the "prince" motor, the needs are different....
I think it says something to the statement of "suggested or recommended" for best power in your manual....
So you WOULD be correct in saying your car runs differently...the computer is retarding the timing, thus making less power.
Just be sure your fuel, typically 87 in Boston, meets what YOUR manual for YOUR cars says is needed.

 

as for what you should have looked at....
Gen2 cars can have an issue with carbon buildup, especially on some cars that are driven for short periods, and not fully warmed up. Might be worth looking into.
The carbon builds up on the intake valves, and CANNOT be cleaned by using a fuel additive....due to the DIRECT INJECTION technology used in gen2 MINI's.....
the cleaning is generally done with either a walnut-shell blasting, or a scraper..manually. It is an issue of sorts for MANY different types of cars of this age-range, and the automakers have been adjusting the technology of direct injection, and PCV valves, etc to reduce the issues on newer cars....

 

If you have not tired this yet, it will perk up your car.

Put some seafoam in the fuel tank !

Read the can as far as the amount, but I usually put 1/2 can into a full tank . . . . .

 

I'll have the guys at Greasy's take an extra close look at my MINI when I go in for my next oil change. I went to my usual gas station, Shell, after work today so hopefully my car will perk right up. I've heard about using seafoam but I haven't tried it. It was definitely 87 octane but I'm still not crazy about the fact that it was used in direct opposition of my request. Thanks for all of the advice guys!

On the bright side, I got a wave from a fellow MINI at the Shell station today