Had oil change on 4/14/16, drove ~400 miles, CE light came up today morning - gas cap is tight - can it be related to oil change? Thanks!

Well, it could be related to the oil change...because some late model vehicles will flag a check engine light if the oil pressure/level is not correct. I would check the oil level ASAP. It is also possible, since all the oil was drained and replace, that right when the tech restated the vehicle, the oil pressure sending unit detected a low condition (momentarily) and thus flagged the code. After you check the oil (look for any leaks as well), I would recommend a hard reset of the computer...so disconnect the negative battery terminal for 2 minutes, reconnect and see how she run. Hopefully the light does not come back on! If it does...it is time to scan the vehicle with the appropriate diagnostic tool...this one should be OBD2 so easy stuff. Lastly, the code may be unrelated to the oil change, and once again the diagnostic scan will be the way to go...find out what that code is! Then you know what to attack next.

Thank you for both. Not sure if I answered here, but the code said that the gas cap has to be replaced. I did not do it, just turned it tighter after getting gas and about 2-3 weeks later the CE light disappeared.