I haver a 1995 Volvo High Pressure Turbo 855 that uses the same amount of oil, makes the same mechanical noises, shifts just the same, steers just the same as the the day I bought it at 90k. It is at 170k now, and has been pushing a 17psi remap for 70k. It rattles more and some trim is getting loose, other than that.. what a bargain. The goal was to go to 200k and semi-retire it or sell it but I think 250k is going to be a breeze.
Improved materials, precise fuel metering, vastly improved tolerances, cooling systems that work much more reliably, continually improved lubricants, the extended warranty marketing battle- lots of stuff has happened that has made 1990-2005ish batch of cars and trucks very long lived. I do wonder if cars made in the last 5 years or so might reverse the trend, as engineering for manufacturing has become close to an exact science, and duty margins (it would seem) can be dialed back precisely for cost savings and still satisfy the marketing need for 100k warranties.
For instance; there was an over sale on extended under-warranty oil change intervals a few years back that cost dealers (the sludge debacle), so that went away, but the manufactures were knowingly cutting vehicle life expectancy once the vehicle was off warranty to make sales and profit.
Add the electronics complexity and packaging density that is pushing cars to the point that even entry level vehicles now sometimes need proprietary OEM equipment and software in order to maintain, diagnose, and repair them and the game changes. This may, or perhaps even has, started ushering in an age of cars the are very expensive to maintain past warranty, as the economics will not work like they do right now because idiotic and stupendously expensive dealer interactions could well be necessary. Which would not work for me anyway.