[e2helper]

But if it is due to that problem you would get a "Check Gas Cap" message in DIC because the fuel system would be detecting a massive "leak" so it is likely not that unless Slickdesi is getting that warning message as well.

 

[e2helper]

didnt even kow the "Check gas cap" was a message.

Yes, if it were the problem you would get that message prior to actually seeing a Check Engine Light. Reason for it is to try to save the owner the time of taking vehicle to the dealer for a check engine light because they didn't tighten the gas cap properly

 

[e2helper]

Speaking of "oil light". What are the factors considered, mileage RPMs, engine temp. ...etc. when the Change Oil message appears?

This likely doesn't answer your question on factors but here is FAQ on what GM calls the GMOLS