Returned home from picking up our '07 Phoenix Cruiser rv, Ford 450 chasis with one of the last 6.0 psd's, built 02/07 and it performed flawlessly during our 2,300 mile trip back home. We took the real scenic route, going through the Blue Ridge Prkway, Skyline Trail and the Cherohala Skyway not in this order-even did Deals Gap, the 'Tail' in the thing!
Outside temps were well into the upper 90's, with one report stating that they had hit 100*, the temp gauge never went over the halfway point (hope it is working

) and for those not familiar with the roads mentioned they range from steep, to very steep and from curvy to very curvy; fantastic on bikes but a bit of a pain in an rv. Yes the cooling fan cycled alot, noisy when on full tilt but the stability of the engine operating temp in this environment impressed us more than the pulling power which was massive.
Fuel mileage was very impressive, in the hills we averaged just over 12 AC cranking ALL the time, and on the main highways through Tennessee and Kentucky; includes alot of hills, we averaged 14.5 (again with the air constantly on) and once we hit 89.81,87 and the Mass Pike we were well over 16 with the last check coming in at 16.88 mpg BUT this was driving very slowly just under 2,000 revs and it was cool enough to check the mileage without the ac on. Consumption was checked by filling to the same visible level in the neck and with quantities of over 27 gallons; I note this to put to rest any questions of inaccuracy due to expansion. This amount of fuel certainly would chill any heated fuel in the tank to make an expansion arugment moot.
Oil consumption nil and the coolant level in the expansion tank remains where it should be both cold and hot.
Talked to alot of rv'ers with the V10-(7-9mpg!!) and we are very, very happy that we went with the 6.0 and the 450 chasis.
The best news for those who don't have one is that Ford is reintroducing the 6.0 in the vans this fall!!!!!!!!!!!!!!!!!!
Tnks to all for a great site and I will post any and all news, good and bad, in the hopes of helping another newbie out.