I ran a porta potty service and one of our 2 trucks was a 2001, 2wd DT466E, 6 speed spicer... 1600 gallon **** truck... . we ran up 100k on it and had to do the water pump, we had off and on again minor oil leak problems on the injector pump, 3rd time at 140k it held, at around 250k, we did the turbo and all the hoses (radiator and pressure) We ran it about 40% of the time on asphalt and the rest on dirt roads. . the guys averaged about 400 miles a day, 5 days a week, 9-10 hour days. . sucked on average 70 units a day. . so there was a lot of time when it sat running the vacum pump at 1800 rpms. had problems on this one with the interior, radio, a/c, electrical... we sold the business, it had 310,000 on it... all we did was run synthetic everything, keep up with all the maintenance... wore out 2 vacum pumps in it... ran real good for us. . just the creature comfort stuff went to hell...
we had a ford F550, sucker truck,4wd, the engine died at 110K, the transmission went to hell, transfer case, a/c brakets cracked, a/c system fauilures. . fuel pump problems, when the second motor started giving us hell, we order another 4wd international with the high output 466E, 2800 gallon cap, a hell of a truck, we put 80k on it the first year, ran perfect for 3 years, 260K... good trucks. . there was a hell of a difference between the first int and the second inter. International paid a lot more attention to the later model, had much better electrical and a/c systems. .
for what they went through (which was day in and day out hell) out here in the desert, they did very well... keep the oil changed and leave em run...