They're great in stock form. Just don't put a tuner on them and push fuel, they're already hot rodded compared to the VGT365 specs that International put into school busses.
We had two 2003s, one was traded in at 180k and one at 280k. Still have two 2007s, both around 150k now. I worked on Fords in a shop though, so maybe what I consider "normal" maintenance would make a regular owner
themselves.
Ford should have put 4.10s in the SRW trucks instead of 3.73s though. Would have solved a lot of the cylinder pressure issues running by cooler at higher RPMs. 4.10s and the factory 275/65R20s would have been a great pairing. The 4.10s in the duallys with 265/70R17s was perfect. But then the trucks would have driven like diesel pullers and not race cars, and trucks driving like race cars is what sells most diesels these days.
That's the truth. Other than people lying about putting DEF into the fuel tank the 6.7s have been a huge improvement. Rusty HPFP = DEF, I can prove it by pulling the fuel filter out. The biggest thing they did wrong was fuel capacity and putting the DEF tank into the same spot as the diesel tank. They should come with 50 gallon tanks.
I got over that by putting a 100 gallon L-tank/chest combo into the my bed, and running a transfer pump into the main tank. I have an 1800 mile range empty, and 1300 mile range towing up to 10k. I put CAT filters into the transfer line that are each better than the stock filters on the truck, that stuff is CLEAN when it pumps over.
I replaced the alternators early in the 2007s, with Leece-Neville 230A units. The 2003s were fine but the newer ones always went through batteries faster, and one FICM had to get worked on. Ed Stefan at FICMrepair did his magic and it's been fine for 10 years now. I did the STC fittings preventatively, but I was already in there for...... something we can't talk about because the EPA will probably throw me in jail without a trial if I talk about it. Had to do one rail plug so far for a long crank.
The worst that's happened to any of them was one truck blew an intercooler boot on the road and the shop insisted that the unison ring in the turbo was sticking because it had an underboost code. No
it had an underboost code, the guy drove it several miles with the turbo disconnected to get it there instead of calling. Could have pulled out an 11mm deep socket and put it back on but nooooooooo he had to pretend he has a functional brain stem and tried to make a decision for himself. I about had a stroke when I found out he authorized the shop to replace the entire turbo with a reman for a cost of ~$1,800 in parts and labor. It's a $160 part and 4 hours of dicking around with the turbo to fix, even IF it was a real problem. Now there's a mystery reman under the hood and someone other than me has touched it. Still mad about that.
Normal Ford BS on all of them though - a brake caliper seized, bearing the in driveshaft rotted, trailer plug wiring is crap and I re-ran it, cab mounts all need to be replaced, yada yada.