I sold my last truck in early November. Bought my first one in 1970.
50 years in the trucking business was about 25 too many. I don't miss it a bit.
I sleep A LOT better at night.
Early on, I had a KW with an 8V-71 Detroit and a Pete with a 335 Cummins.
Later on I had 3 COE Petes with 425hp 1693 Cats. Those ware all mechanical, dual overhead cam engines, and put out LOTS of power after you adjusted the rack stop screw on the injection pump. Fuel mileage sucked though, but fuel was fairly cheap.
Then came a few more Petes with 3406Bs, still mechanical engines, lighter than the 1693s and pretty good power. They were also better on fuel, usually 5 mpg or a little better average. I tried a Detroit Series 60 475hp in a truck, was a pretty good engine until it spit a rod out the side in St. Louis. Replaced it with a 379 Pete with a C15 Cat 6NZ that went 1.5 million before a broken valve actuator caused some problems that ended up having to overhaul it.
The C15s are basically an electronic 3406. Whereas 3406 injector nozzles were ~$75 each, a set of electronic injectors for a C15 was $4K.
The other weak point with electronic engines in a truck is the wiring harnesses and sensors. I knew when they started using electronics on engines, that once they got a million miles or so on them, they would become problematic, and they were. The C15 developed an intermittent miss, and I spent over $3K at Cat shops trying to find the problem. Finally found a harness worn through inside a loom clamp behind the air compressor. I told them to change all the engine harnesses and be done with it.
The last truck I had, an '07 Pete with a C15 twin turbo 500 hp Cat, was overhauled at 1.2 million after the idiot driver ran it low on water and got it hot causing the head gasket to fail. Then after another 50K miles it went spastic and ran like shite. After a 100 mile tow to the Cat shop they found some oil had somehow gotten into an ECU connector and caused the problem. I thought oil was a pretty good insulator, but apparently ECUs think different.
The new engines with DPTs and DEF injection can be nightmares. I have a friend that bought a new truck a couple of years ago with all the emissions crap on it and he's almost ready to get rid of it and find a pre-2008 truck or build a glider kit with a C15 or ISX. He's tired of some sensor going titsup and having to limp it into a shop to get it fixed. So far it's been under warranty, but that's running out soon and he's not going to put a bunch of his money in it to keep it running.
All in all, I think the earlier electronic engines were pretty good. They weren't all that complex and did give better fuel economy. But when they had to add all that Tier 4 crap, it was a step backwards.
And don't get me started about the ELDs. That was a 25% decrease in productivity slapped on the independents and smaller operators..