I guess the traditional way to gauge wear and tear on an automobile engine is by the number of miles the vehicle has travelled. But I know that wear and service life are measured in hours on airplanes and other motors that run at a constant fixed speed.

Which is the more reliable (and accurate) way to measure wear on a car engine? Is it possible to determine how many "hours" an engine can run at a certain rpm, e.g. 3000 versus 3500?

Hypothetical: If you took a brand new engine (say, for sake of argument, a rebuilt b230f) and ran it constantly at 3000rpm (with a constant supply of fuel and lubricants), how long could the motor run before top/bottom-end work is required?

I realize this is kind of "out there" as these things go, but I thought that maybe one of our resident engineers had already done the requisite calculations. ;-))

-jim