[Gunner]

Engines in the 1960s typically needed rebuilding around 75-80k.* Engines today can typically run over 100k without even a tune-up, and close to double that before mechanical or smog failure forces rebuilding. I'd say that answers the single-weight question.

* Yes, you could keep driving them for 50k after that, if you didn't mind the mileage hit, oil burning and smoke.