It would be interesting to see comments regarding comparative longevity/reliability of different gas/diesel engines, from professional mechanics, who provide service, for both gas and diesel powered light trucks, ie; pickups.
It's interesting to listen to owners, but I, myself would also like to hear from mechanics out there who also have experience working with light truck engines.
I have a feeling that modern diesel and gas engines are both capable of lasting for 250,000 to 300,000 miles of hard work, with good maintenance and little other than factory recommended maintenance and not much replacement of parts, other than service items.
Back in the late '90's I was running in one vehicle of mine, a Chevy Vortec 4300. I asked the dealership mechanics how many miles I could expect out of this engine. Their reply was that it was quite a little workhorse and it wasn't that unusual to see them come in for oil changes, etc. in light truck/vans used commercially...with well over 250,000 -300,000 miles with little repair needed in that lifetime.
I also recall a newspaper article in my berg that had a story about a early 90's Dodge with a Cummins diesel. That truck was used to ferry trailers from Indiana to points across western Canada. The owner/operator took it to the same local dealer for oil changes/required maintenance. It had well over a million miles, last I had heard of it.
I think it is almost a rule of thumb that modern light truck engines whether gas or diesel, can run up very high miles, with little other than factory required maintenance.