When i purchased the car, premium gasoline had been used on it throughout its lifespan. However due to my restricted budget and rising gas prices, i have been forced to put regular in lately. After a few tanks, the check engine light came on, and has yet to go away. My friend has a 2003 Acura TL that was supposed to run on premium, was filled up with regular, and its engine started knocking and his check engine light came on. Could this be the source of my problem also?

 

Go to AutoZone and have them check your codes for free. It could be as simple as your gas cap not being tightened correctly. Codes first.

 

I run regular on mine with no problems, get the codes and then go from there. There are way too many different reasons why the CEL might be on.