I bought a diesel in 2013. Ford. 7.3. It was 10 years old at the time and had just under 100,000 miles on it. Fine with me. I'm familiar with the engine and the truck so I couldn't pass it up as a straight trade for my old truck which had IIRC 371,000 miles on it.
It tows ok.
BUT what I learned about owning diesel is that everything you do costs more. Sure I get somewhere in the vicinity of 19 mpg average with it with no load on it, and yes it's supposedly "bulletproof". However that all pales when it comes to repairs. The first 100k that I owned it, zero issues. Not even brakes. 2 sets of tires oh and by the way most diesel pickups eat tires (weight?). I rarely get more than 30,000 mi out of a set, and it's over $1000 for a set now. I did regular maintenance more often than I probably should have but I know they're expensive to fix so I keep up with it.
It currently has 240,000 miles on it, well almost. Close enough. I still drive it.
At 220k I noticed that the coolant bottle smelled of diesel fuel. Injector cups leaking. I simply don't have the time to fix it myself so I called a shop across town, I know the owner really well and we do some horse trading a few times a year. $2750 to do cups and majority of it is labor, the cups are like $200 for a set of 8. Then 8 gallons of coolant, 5 gallons of oil, gaskets, o-rings, etc. Injectors are getting weak, so I priced those too. All told, for cups, o-rings, and injectors I'll be well over $6000. Keep in mind, these are wear items meaning it'll have to be done again at some point.
That's not to mention that every oil change is over $200. The fuel costs $.50 more per gallon than 87 octane gas. That's starting to narrow up a little now that gas is up around $3.00/gal. The air filter is $60 (aftermarket) thankfully it don't have to be done very often. Transmission service $250, every 30,000 miles or so. Two diffs to change fluid in. Transfer case. Of course those don't add up to much, but everything costs more nowadays and my pay hasn't increased proportionally, and I think I share this with many.
So with just the repairs, it'll cost more than the truck is worth. Not counting maintenance.
--And I don't have DPF or DEF to deal with.
Shop truck at work is a durmax but a 3/4 ton 6.6. They just had to replace the def tank as it was leaking, and it was $3700 for part + labor (dealer). DEF is a maintenance cost that must be figured in to your fuel. Sure you might get nice fuel mileage but add in the cost of def to the fuel over however many miles you get out of a tank of def and while the MPG is impressive, the cost per mile isn't any better than a modern 1/2 ton gas burner. Perhaps that's why all the UPS and FEDEX local delivery trucks are gas burners here. I mean if any company has costs figured out, they should and with them switching back to gasoline, it tells me a lot.