>Servicing of engine internals. A car would be down on power significantly after 10 years of wear and can be restored by adjust valve clearances, replacing seal

>Servicing of engine internals. A car would be down on power significantly after 10 years of wear and can be restored by adjust valve clearances, replacing seals and piston rings, cleaning parts, etc. This has been functionally debunked by hundreds and hundreds of YouTube videos by dozens of channels who buy bangers and put them on a dyno. At 10 years, usually only 3-5% power reduction. 20 years? More like 5-6%. I'm not talking about spring chickens which were babied by retirees, either. I'm talking cars that clearly have had a hard life with tons of deferred maintenance.