I accidently put the lowest grade gasoline in my 1999 C230 Kompressor. The check engine light came on and the engine has been been running rough. It does not always start on the first time I turn it on. I have since put several tanks of premium gas but the engine still runs rough and the check light is still on. Any suggestions?

 

take it to Autozone or similar auto parts store and have them scan your codes (free). the code may lead you in the right direction

 

Did the check engine light come on during the time the low grade gas was in the car? Sounds to me like you may need a new MAF, which is super easy to install. That fixed my rough idle and turned off the CEL.

 

Easy to fix but an expensive one.

 

IMO your oxygen sensor are out last time my 99 c280 got check engine light on my mec. replace the two front oxygen sensor the problem gone.