[yason]

If cars are getting 20 times more use they will wear out much more quickly than they do now.

This is just a matter of the practical design choices. Any machinery that is in heavy use usually gets fitted, appropriately, with more robust set of parts which last many times longer before wearing out.

Current consumer cars have bearings, joints, and moving parts that are carefully optimized to match the expected usage pattern (which is mostly idle) for a designated period of time and nothing more. That's why older cars can sometimes run for ages. Decades ago we didn't know how to make extremely light-weight parts from least amount of steel with a calculable expiry time of, for example, 40 thousand miles so engineers had to fit cars with slightly heavier and more expensive parts to make sure they didn't break too easily. Think about fitting bearings and joints from a heavy van into a light Japanese small car. Or consider old 70's-80's Saabs and Volvos that can last nearly forever.

Likewise for fluids and lubrication, it's easier to clock high mileages with a car that is mostly in use throughout the day rather than with one that is used a couple of times a day for commuting. The engine wearout is at its peak during the first miles after a cold start.

[rdl]

Also, the 1970s and 1980s were a low point for cars in general -- lots of new environmental regulations were kicking in (including a whale oil issue which was discussed on hacker news), causing objectively worse reliability for many cars in the 1970s and 1980s vs. the 1950s and 1960s. By the late 1990s the Japanese and German manufacturers seem to have resolved things, and by the 1990s, the US automakers.