If a diesel is properly maintained, instead of just changing the oil when it gets thin, it is possible to get many hundreds of thousands of miles out of it. However, not babying the engine, and keeping levels constant and fresh will cause excessive wear on the engine, and significantly shorten it's life.

The powerstroke could be expected to run for 400K miles, if treated well. There are plenty out there that did not get much past the 200K mark,because of lack of proper maintenance. I had an old perkins engined truck with 500K on it, when I sold it - still running strong.

Wm
'02 F250 4x4 Crew Cab Lariot; white with leather - 3.73 gears. Not yet modified but the accessories are looking good.
'96 F450 4x4 Crew Cab XLT; White with Grey interior. Banks Turbo, Intercooler and Exhaust,
Power pack Chip, shift kit, Auxiliary transmission, electronic enhanced transmission control,
16 forward and 4 reverse ratios. 340hp 660ft lb, 4.10 gears, 12,ooo# winch