Just bought an 06 mini cooper. The gas cap is not creating a very tight seal and so fuel can leak out. I especially notice this when I top it off or drive on the more fun side. I guess the easy fix is to drive a little more mellow and don't top it off but it would sure be nice to replace the old cracked o-ring that I'm sure would enable me to do both with no leaking. Anyway, called the dealer and was told I can't buy a new o-ring I have to buy the entire cap! Anyone on here know where I can get an aftermarket o-ring?

 

The cap is right here. I would just do the cap as the sometimes these things can go bad internally and then you get the check gas cap warning on the older Gen 1 MINIs. Also the o-ring if you find it has to be one that can resist gas and checmicals. MINI does not sell a seprate o-ring and I could not find one aftermarket.

Usually, if they just replace the whole cap , it's fine. Make sure you insert it straight and turn and click.

16117222391 Gas Cap

http://www.ecstuning.com/Search/SiteSearch/16117222391/

 

One tip...
Do not "top off"
Overfilling can stress the emissions systems and cause early failures... gets $$.
Fill it to the click...maybe two or three....but dribbling that last bit of fuel in can flood the carbon canister...and you will start throwing codes....it dies get "dried" out...but saturating it a few times by overfilling with cool fuel, that then expands as it sits in a car can cause issues....and if fuel is expanding out the gas cap.... WOW!!
If the o-ring is bad, you will get an emissions code...due to the tank not holding vacuum so the system will detect it is not airtight....
Every 5-7 years, a new cap is not a bad idea....