I use Mobil 1 0w-30. Supposed to promote fule milage and as I live in the mountians of tahoe works great for cold starts. It is the flagship oil for Mobil 1 from the literature I have read. Why synthetic? Better viscosity index improvers, less apt to foam. Less likely to oxidize. Also has the highest cold flow rating, and a really high heat capacity. I also put syn throughouy vx and it runs quiter and improved the rolling resistance especially when I did the front and rear diff. They stress not to use additives- I don't. They say the break in thing is a myth. It is used on many new cars for break in like Chevrolet (Vettes), Porsche, and AMG/Mercedes. Good enough for my so I drop the extra cabbage.