Car engines don't operate at full power (or some high percentage of full power) then 55%-75% for hours on end. Car engines rarely see full power, let alone operate continuously above 55%. My car specifies 3000miles between changes. Conservatively choosing 30mph average speed (and for easy calculation) that's 100 hrs of use - and not even above 50% power for any of it.
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My bike specifies 10,000 km between changes, is a small, light engine producing 160 HP, runs at ~50 - 60% power a lot of the time (on motorways) and gives no problems... but it is new technology, fly by wire throttle, electronic injection, etc.
it is possible with airplane engines too - sure the new rotax engines will prove very reliable for instance... just need more competition and volume in engines to spur the manufacturers on - what's the point in adding 20kg to make an engine that only needs an oil change every 200 hours, when regulations will make you inspect it every 50 anyway.
Alex
P.s. how do you quote in a reply?