Comment by vel0city

> As for other stuff, work on cars for few decades

That's the experience I'm drawing from when I point out that "virtually no other part degrades in performance the moment you use it" isn't based in reality. Everything is constantly wearing out. Anything rubbing on another thing, any fluid being pushed through a hole, anything that might be reacting with another thing, its all slowly getting more and more out of spec. And when it gets more and more out of spec, its performance gets worse. You might not immediately notice it, that performance might not be in the go go kind of performance, but it isn't working as well as it used to.

Are you really going to tell me a car with a couple hundred thousand miles on it running all original parts (assuming they didn't literally break apart yet) is likely to be anywhere near the same performance as when the car had 200 miles on it? Its not. Its almost like there's a reason why mileage is considered when people price cars. The suspension isn't going to keep the wheels as well planted, the cylinders likely don't have the same compression, those fuel injectors are likely tired and aren't spraying optimally, that coolant pump is worn down and barely able to pump coolant anymore, your timings are likely not optimal anymore due to slack in the timing chain or belt, your spark plugs aren't making as full or reliable of spark, etc.

If your response is "well you would have replaced those by now"...well, why would you have to do that? Because they...had their performance reduce over the life of the part?

And even then, a part of that break-in period of those parts is the part's performance actively changing over the life of the part with pieces of the part literally degrading, just pretty quickly and positively for performance as opposed to negatively. That positive slope of performance change is a pretty early hump though, otherwise as I mentioned you'd be taking me up for ensuring all your tires are near-bald (but not quite, they haven't actually failed yet!) all the time and you'd be dumpster diving for the good stuff out behind your auto parts store.