I have an 03 F250 6.0 PSD with 125K on the clock. A lot of that mileage is towing my 8500# trailer all over the east coast. I have had very few problems with the truck, just emissions recalls, and one other warranty item. The truck is a beast..it tows my trailer like its not even there.. though the brakes could be a little better. Change your oil religously.. (all 15 qts) it really makes a difference.
The 6.0 is really a complicated pieces of equipment, hence following the maintenance recommendations is uber important
I get 15-17 mpg around town, 20-22 mpg highway. and 12-14 mpg towing. It tows better than my friends 04 Dodge Cummins, gets better mileage than the cummins, and has a much better transmission than the dodge. The Ford tranny is a 6 speed, though it only uses 5 of the gears...actually its a 3 speed with 2 final drive ratios, and selects the gear based on load.
QUOTE
You can run biodiesel in the 7.3, but the 6.0 can't handle it..
I run B100 in my truck every opportunity I can. If Bio is avalable I fill up with it. Bio has higher cetane than dino diesel
Though this truck has been great for me, when I buy another tow vehicle it will be a Duramax (Izusu) with Allison transmission.