While in college in Oklahoma City I always went to the dealer to get my car serviced and they would put the right oil in for my car which is 5W-20. After returning home from graduation and driving all the way back to California with it and recent service from that dealer I have just noticed that they have put 10W-20 Oil in my car instead of 5W-20!!! Does this matter and what should I do because I am actually in need of service right now for an upcoming road trip???

 

They put in 10W-20 engine oil? Can't say I've ever heard of 10W-20 oil from any manufacturer (there is 10W-20 hydraulic oil out there but that should never-ever be used in an engine); are you sure they didn't put in 10W-30?

Either way, for the summer months it probably won't make too much of a difference, however, 5W-20 (and to a greater extent 0W-20) will provide better cold start protection for your engine, even of the Outside Air Temperature (OAT) is above one-hundred.

 

What he said ^^^^