As a corollary, consider how much fuel (particularly diesel) and much more than that oil (lubricating oil) have bettered around those times.

AFAICT in "practical" mechanical engineering tribology:

https://en.wikipedia.org/wiki/Tribology

is one of the fields that made the most progresses in the 90's, thanks also to the introduction on the market of totally or partially sinthetic oil, that literally changed the game when it comes to car engines duration.

The (huge) difference in spark plug life depends more on electronic ignition, of course and that also became mainstream in late 80's and 90's.

When it comes to water pumps, allow me to disagree, however, once upon a time if a water pump leaked you just changed gaskets and maybe the ball bearings, since around the same time you are often forced to buy a new "whole" pump as they are not any more serviceable.