Volkswagen uses synthetic 5w40 from the get go dont they??? and I know the cobalts SS come with mobil 1 and every oil change is reccomended use of Mobil1 (wonder how much money they made off that lol) I have an 07 Classic Silverado, i did my first oil change at 2500 KMS, Synthetic Mobil 1, and then right after my dad thought he was doing me a favour one day when he took the truck and took the free oil change coupon they gave me, it was time for one (every 5000kms is what is reccomended here), and he got my oil change done, of course a free oil change wasnt synthetic. I started to watch the oil gauge. Man what a difference synthetic makes, my truck with synthetic, would idle at 150ish and when i was pushing the gas it would be at 275 (normal operating psi) with the regular AC DELCO oil, my truck would ilde at like 250-275ish and when it was going would go near 350ish! as soon as i seen that i said screw this fresh oil or not i changed it 3000 kms later, and my chevys seem to like fram double guard (made specifically for trucks i believe) (synthetic filter i think too)