Lets assume you have a new car and drive very little...
Oil "wears out" over time once used at all.
Example: If you only have short trips can be worse because oil can't get hot enough long enough to drive off moisture and gas that blows by the pistons.
Belts "wears out" fast if pulleys rust or oil and other crap on them.
See my Cave,
Serpent Belt Most applies to V belts too.
related...
Water pump, brakes and some other parts don't like not driving for weeks or months.
Coolant and Brake Fluid keeps a microscopic film in normal operation on WP shaft and Brake (and clutch) pistons to lube and protect the seals.
Now add 10+ year old cars often have weak coolant, wet brake fluid, and other issues making more problems.
50/50 coolant mix can be weak after 3 - 5 years because rust blocking etc wears out even parked. See my Cave,
Coolant Fill (You can't use Dexcool and others in cars that have "Green Coolant" and think will last longer then 3-5 years.)
Brake Fluid gets wet sucking water from air thru every tiny seem and worse if has damaged rubber hoses etc.
------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)The Ogre's Fiero Cave[This message has been edited by theogre (edited 07-05-2020).]