I have a gas V10 Ford, and I change the oil every 3,000 miles or 1 year. I don't know what my manual says on reccommended time or interval, as I have never looked. I usually find the factory limits are beyond my limits. My manual calls for a high quality oil but it prefers synthetic. I use Mobil1 5w/20 or 0w/20 (if I can find it) at the recommendation of a Ford service manager.
I am probably overdoing it on oil changes, but as hard as these engines work, and the heat they create, I figure better safe than sorry....
2005 Gulfstream SunVoyager 3861LTD
Ford chassis, V10