gotta add my two cents -- really reiterating what has already been said....
The 6.0 PSD is a beast! When she's running as designed you just can't beat the performance and torque. That being said she demands lots of preventative mx (think $$) to ensure she's capable to perform. I can run my 6.0 with my AF990 fully loaded wide open in the hot desert heat. But I also know based on my exhaust temp when to back off too.
Some keys to ensuring longevity if you're using it primarily loaded up with a camper and even hauling is:
1) Engine monitoring is an absolute must. You have got to have eyes on your engine oil temp and coolant temp as it tells the health of you oil cooler. I monitor fuel pressure, EGT, and many other variables which will just make this post loooong. Get a DashBoss and you can read it all on your iPad as you cruise down the road.
2) Add a fuel additive every fuel up – I use opti-lube
3) Change your oil at 3-5K (I base it how hard I've been running it) to prevent oil viscosity sheer and breakdown. I use a synthetic (do your own research) others use dino oil. The key is to change it if you're working it.
4) Add an engine additive to prevent injector stiction.
5) Next, flush all the Ford Gold silicate coolant out. After its been flushed and cleaned add an ELC Coolant (most will last a good five years of 300K miles)
6) And then add a coolant filter. At first change that out at 500 miles. Up the frequency after you start seeing less and lees filter contamination (yep, cut off the top of the filter and inspect the accordion paper).
Mine is all stock but trust me it’s fine for what I use it for – camping and hauling. I’m always keeping track of engine health to ensure the EGR is still operating (I have to get SMOGed every year). Do your research and you’ll have a phenomenal platform able to tackle any obstacle.