Why do diesel engines seem to outlast gasoline engines? Shouldn’t they be built with the same stress safety factors built in and fail at around the same rate?

Question

Edit: Specifically referring to passenger vehicles and consumer trucks, not commercial vehicles that i assume would be built to go much longer anyway.

In: Technology

Answer 1

Gasoline engines usually operate at 25-50% higher RPM and have longer piston strokes further increasing piston speed which causes increased wear on pistons and cylinders as well as stress on the connecting rods. Both rods and pistons also have to be lighter to accommodate the higher speed. Diesel engines on the other hand have to be built stronger to allow higher compression ratios that can auto-ignite the fuel.

That being said I doubt you will see very significant differences in lifespans of modern engines that are properly maintained. Maintenance is probably the biggest factor that increases lifespan of commercial vehicles that have to regularly undergo it while passenger vehicles don’t necessarily do so. And this is probably where the greater robustness of diesel engines might allow them to better cope with lousy maintenance.