SES light on, what do I do?

I recently purchased a 98 Buick Regal three weeks ago and it had transmission problems but that problem was solved when I switched to a different brand of gas, now the SES light is on and I am confused of what to do and what caused it to turn on. I don't want to spend a lot of money trying to fix this car, is there another solution?

Welcome to AF.

The only way to tell what turned on the SES light is to get it scanned. Places like Autozone or Advanced will do it for no charge. After getting the odb-ii DTC error code(s) then you can determine what the cause is or a course of action.

You've been using premium right? Have it scanned. I have 20 bucks that says it's EVAP related. Usually a leak somewhere. Check or have someone check the vacuum lines at the EVAP solenoid (check diagram near driver's headlight under hood for helping in locating). Is the gas cap tight or an aftermarket locking type? Let me know what code you get.