Re: Synthetic Oil Change Interval on the V10's
Depends on your driving cycle. Of course Ford's official word is 7500 miles using 5w20 synthetic blend.
I've gone as long as 12,000 miles on full synthetic with 100% towing miles. I actually go more frequent when I'm not towing because it means more in-town driving. If it's all commuting miles, then I switch back to the blend and do it at 5,000 miles. Full synthetic has better tolerance against thermal breakdown and wear/shear, but it still has no more resilience against condensation which form during warm-up, so that's why you can't stretch it if you are doing a lot of short trips.
If I was doing all highway driving, not towing, I'd probably stretch it to 20,000. But that's just personal opinion. I don't think any of the OEMs have an official stance on extended oil change intervals.
My brother's co-worker found out on his 5.4L that 79,000 miles is too far. He thought the 100,000 mile tune-up schedule included oil changes.
2000 E450 dually V10 wagon