From personal experiences with our work vans ....
Peugeot boxer at 80 odd thousand cold start sensor failed
Injecting extra diesel into engine and diluting the oil and locking the engine
Citroen relay 70k and headgasket failed between water gallery and oil way
Dumping coolant into sump locking the engine
All motorway miles and serviced as per manufacturer's .
Our local pug dealer says no further than 10k between services and ideally shift on before 80k or expect bills .
Next van will be a sprinter/crafter .