I think everyone can agree that the worst older automotive abomination (or at least GM's) were those Oldsmobile diesels in the late '70s or '80s. Because those brain-addled, idiotic, shitheaded, cretinous, drooling-vegetable morons thought it was really cute to take a V8 GASOLINE block and put diesel heads on it (!!!). Which means the bore and stroke were all wrong for it to ever run correctly as a diesel. Its water jacket system was too small to disperse the extreme extra heat of a diesel. The crankshaft, connecting rods and bearings, and general metallic structure of the engine parts weren't anywhere near thick, heavy and reinforced enough to withstand the extreme extra torque of a diesel, so it had this adorable habit of throwing a rod at 40K miles. I'm sure it made an interesting, very expensive-sounding noise when it did so.
My aunt and uncle had an Olds diesel station wagon in the early '80s, it always spewed a giant, angry-looking stream of black smoke behind it - much like the starship Enterprise "tracer stream" when it goes into warp drive - and it had that 40k mile lifespan. Which was so rampant at the time I think they were recalled at some point but I don't remember for sure. That experiment certainly didn't last long. I've never heard of one of these unholy gasoline/diesel miscegenation engines lasting any longer than that forty thousand threshold.