15 W 40 or 5 W 40 oil for the 6.0. I use synthetic oil (Rotella T) and change it every 5000 miles. I can get the oil at Wal Mart for $18.99 per gallon, I think.
I just happened to be looking yesterday at oil and saw the prices. Wish I had some cash I would have bought out all the Mobil 1 diesel the store had on the shelves.
Thanks for the feedback guys. New to this diesel thing. Always owned F-150's. Just knew I wanted a Super Duty. I'm catchin' on quick. Thanks again for your help!
Running Valvoline Premium Blue 15w-40 in mine year round and yes it will start in -20* with out being plugged in and my truck has 168k on it. It's not happy when it starts but it starts.