Hello,

I'm a proud owner of a brand new mini cooper and while I was getting gas today, I accidentally used 87 unleaded. Now, my mini is not going as fast and its putting, like its having a hard time accelerating. Will this affect the long term use of my car? Please help! Thank you...

 

NO the engine has retarded timing to prevent detonation , so you are likely OK.
You can either go to the parts store and get some octane booster and pour that in the tank , or run the tank down and use some premium to offset the regular

 

yaa octane booster should help but you should be okay. once your tank is down to half or even 3/4 full put more premium in to help balance it out i wouldn't worry too much about it though just as long as you don't do it every time