: V6 STS - Oil Type?

07-09-07, 07:20 PM
Just curious what oil comes in a V6 from the factory. Per my owner's manual, the V8 takes synthetic, V6 fossil. Yet..........the oil filler cap on my V6 engine says "Mobil 1 5W30". I always use full synthetic in all of my vehicles anyway, so I'm not asking what oil I should use--just wondering why the cap does not match the manual.

Plus, my first 2 oil changes are free as I have coupons from the dealer. I don't know what type of oil they will use, or if I will have to pay the difference if I want synthetic. Car only has 2600 miles on it, so haven't had first oil change yet.

Number 3
07-09-07, 09:14 PM
Well, I asked the dealer and they told me they used syn. I hope that helps!

07-09-07, 11:59 PM
I've had this engine in both a 2004 CTS and now a 2007 STS. It takes synthetic oil. I haven't checked the manual, but the dealer will follow what's printed in the engine compartment. That is the authoritative source. It is common for a spec change to be made to a vehicle or engine that doesn't get reflected in the manual.

07-10-07, 12:02 PM
The GM Oil Life System will be reliable only if full synthetic is used.

07-13-07, 08:58 PM
My Dealer states it's Mobil 1 even though the owners manual says that V6's don't need it. And that's what they put in.