buck, did you use vtec try using vtec after the oil change? did you check the oil level? it could be possible they didnt put enough oil (our cars tend to take more than the avg 4cyl) and if you tried to use vtec without enough oil it will through a light, but you wouldve known by vtec not engaging. If you think its a not a coincidence then check the oil level, thats all they really couldve messed up besides using the wrong weight. Did you keep the light on or did you clear it already? if the light stayed on and you dont know how to pull the code to find out what it means I could tell you how....