Ron,
I also have the Excursion. 2002 diesel chipped. 30' trailer with two cars and a chassis hanging above. 55k miles now. No problems. Running on
synthetic. Drive the car every day back and forth to work and all over the country doing stuff. Power is unbelivable. I don't have any knowledge of others but can vouch for the ford power stroke. Oh fuel mileage, great around town, above twenty, on the road 22 or better, doesn't care about mountains very much. Pullin' trailer with big load 14-15mpg.
Good Luck
Chuck