I have a 2000 Camaro Z28. It only has 29,000 miles and has been kept up with no breaks except the power window motor. Last summer my "check engine" light came on so i went and had it tested. THey told me it was bad gas. THey said to run it out and put new gas in and maybe a gas treatment bottle (STP Top Fuel). I did that and my light went out. Recently, every time i fill my tank and run maybe 20 miles the light comes back on. I add a bottle of that stuff (stp, or dry gas or whatever) and it goes out. Has anyone else experienced this?? I read what i could find and the computer in the car reads the quality of gas and even going from Premium to Regular could do this. I never use regular, always premium, but it appears to be the same anymore. I hope this makes sense. It really angers me to think what i suspect and know there's nothing i can do about it. As high as gas prices already are, i have to buy gas cleaner to put in a fresh tank. geez!