Just got a new (2003) Mini with only 34,000 miles on it! On the way home, it was dark and I put regular unleaded fuel in. I noticed her running a little rough and found out through my owner's manual that I must use super unleaded. Have I done any harm to my baby? Should I add octane boost? Should I just fill it the rest of the way with super? Any help would be appreciated. Thanks!

 

Welcome to NAM.Your MINI will be fine.

 

FWIW, the engine has a knock sensor in it and will pull timing if it has problems. When you're at half a tank or so, fill er up with the good stuff and go on about life...

Matt

 

Yeah you will be all right, if you have used some of the reg. unleaded top off with some super premium, and then when you have run another 100 miles repeat, another 100 and repeat, you will have about 75% premium then. Enjoy..

 

FYI, if you are interested, there are a bunch of posts on this forum about which brand of premium gas to use. I've been using Shell, and pulled up to the pump last week, wasn't paying attention, and almost put diesel in my Mini. OOPS!

 

I almost did that once, 2! LOL! Scared myself 2 death! I'm a regular Shell user, as well.

 

you could buy octane boost at your local parts store to help out if you are that worried about it.

 

No need to freak out. Just top it off with some fresh high octane fuel as soon as possible. Also, the ECU will be yanking the ignition timing automatically if you push the gas pedal too hard to keep the engine safe and avoid detonation. Just take it easy on the car with the lower octane fuel.

Shell and Chevron are generally considered to be top tier fuels. So, go get some of that good gas to mix with the crummy stuff, you can also put a bottle or two of octane booster in if you are really nervous as previously suggested but that really does not make much of a difference.

 

Agreed with others. Just accelerate as easy as possible in traffic. Either top off tank with premium at your earliest convenience (maybe 3/4 tank mark), or get an Octane booster at an auto parts store.

 

wait a minute here i just but a 07 mini cooper s so what type of gas should i be using 87 or 89?

 

ALL Minis use premium gas, regardless of whether it's an S or not.

 

91 or 93

 

****... 91 or 93

 

yup. ive done 93 every tank, except once when they only had 91

 

Check your Owner's manual.

87 is too low.
89 is still too low.
91 is the minimum requirement, some regions can get 93, get that for the best performance

 

However........

When I first got my '03 MCS JCW I was having cold start issues, where it would start but run rough, on a restart it would run fine. The dealer told me to run a tank of 87 thru it, which I did. Now, it was the dead of winter and cold as hell, but it fixed my problem - I also never ran any more thru it.

Bottom line, do not worry about it, use the car normally and when the tank is empty fill it up with premium again. Don't bother with additives or adding gas every time you have room for a coupla gallons - you'll be fine.

 

Since nobody mentioned it, I'd say dont worry about it. The car'll be fine. =o\ =o)

 

My cold start issues were based on the gas I put in my MINI. Turned out to be Hess gas. Never went back; never had cold start issues again.

 

She'll have the super juice from now on. Wasn't that worried about it, just more of a duh on my part as I noticed it states to use Premium fuel inside the gas cover. Great Mini'n!

 

Slightly off topic, my town has some 100 octane for $6.50/gal. Will I notice a difference? Would it do any good? Will it be the most fun commute ever?

 

WOW is the 93 going to give me better gas milage?

 

From what I have read, using any higher octane than what is recommended will not do anything special. 91 is recommended, but unfortunately I can only get either 89 or 93, so I'm using 93. If I could get 91 I would. Maybe I should do half a tank with 89 and top it off with 93!

 

It makes the most difference when you are pushing the car hard, when the head temps are high and detonation is most likely. Very spirited street/twisties driving, or even more likely on the track.

Having the highest possible Octane fuel will allow the ECU to run maximum ignition timing and therefore you get maximum performance. The MINI has a knock sensor that tells the ECU when the timing must be retarded to protect the engine.

If you have a very light right foot, you and your car will never notice a difference in 87 to 93 Octane. Still MINI recommends premium fuel, so get the good stuff.

 

Agreed with MINI Racer. The main reason for a higher octane is to create a slower burn of the fuel, which is why you can create a longer spark advance. Old-school motorheads could advance timing anywhere between 36 and 42 degrees using 93 octane fuel and a fairly stout V8. Of course, less timing is used with boost-fed engines, or you will get massive detonation. A side benefit of a higher octane is it usually burns cleaner because it's more pure.

Stock MCS' are tuned for 91 octane. Most tuners will reconfigure the computer to require 93 octane, so you can then take benefit of the extra two points.

 

Your car will be fine with regular. It just won't make as much power as the computer will sense the lower octane and retard the timing to compensate. Just fill it up with super on your next tank and it will be fine.

As for running 100 octane, I doubt you'll feel any difference without addressing the software and/or boost level. See if you have a Sunoco in your area. They usually sell unleaded racing fuel if you feel like seeing if it makes a difference. High octane racing fuel is a bit harder to come by in SoCal.

Also, do not run 100LL or Avgas 115. These fuels contain lead and are for use in air cooled aircraft engines. The lead will destroy your catalytic converter.