I'll try to answer the original question from a historical standpoint. Diesel trucks became popular in the mid to late 1950s, or about the same time the railroads went to diesel-electric. Before then, trucks were mostly gassers. Three to five mpg was the norm for a gasser semi-truck.

Diesel truck engines, in the US and Canada, didn't really change much until the advent of "low sulfur fuel" and de-regulation. The combination of low sulfur fuel and better generations of lubricants over the years meant that a top-end overhaul went from 300,000mi to a look-see at one million miles. Bottom end went from a look-see at about 750,000mi to a look-see at a million, or when the pan gasket goes. Better materials (steels, gaskets, etc.) over time also helps here.

Deregulation drove the fuel mileage up. A road truck used to get 6-8mpg. Now 10-13mpg is the norm, thanks to new injector pump technology and computer controls. The old trucks used the same technology as our old MBs. New truck injector technology varies, but a common high pressure manifold downstream of the "injector" pump and computer controlled electric solenoid valves for each cylinder is an adequate first description.

Why do trucks last longer? The old trucks didn't. They just had parts replaced on a schedule, for the most part. Water pump would be a good example. Overhaul schedule really isn't much different than for an older MB.

New trucks last because:
1. Engine rpm kept within a 600rpm span, with multi-speed transmissions.
2. Huge air filters, as compared to a car.
3. Multiple large oil filters. My last truck took a gallon of oil to fill the two filters.
4. Some trucks even have coolant filters.
5. Bigger fuel filters.
6. Fuel-water separator. This is the key difference. Diesels don't forgive water in fuel. Truckers figured it out, most car drivers haven't (yet).
7. Better held maintenance schedules because of the capital cost. A rebuildable engine is worth as much as $10,000. Scrap metal isn't worth diddly.
8. Better education of drivers. A truck down for unscheduled repairs doesn't make money and neither does the driver.

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daBenz - 1970 220D