Hey Scotty! Wouldn't those stupid obnoxious beauty covers that you hate cause heat to stay trapped under the plastic?
A tiny, tiny bit. Which would actually help it get up to operating temperature quicker.
But the engine is cooled by water, and the thermostat regulates the temperature of the engine so beauty covers won't make it overheat.
They're pretty useless overall. I've never owned a car that came with one but I'd toss the cover in the trash if I did.
Read with more care, people. The question is about heat. Not whether or not you like beauty covers or find them useful.
They don't trap enough heat to worry with and do help keep dirt/debris from collecting in irritating places like the engine valley, etc.
That said, I typically leave mine in place. If I'm working on my car so much I'm tired of pulling the engine cover, it's time for a new car.
Those plastic covers wouldn't be put on there if there was a danger from them holding heat to the engine. The engineers knew what they were doing when they made them, and probably hate the industrial designer who came up with the concept because it has next to no mechanical value on the car, and some corporate clown thought the sleek appearance would sell it, so they had to make it work.
My BMW mechanic tossed his beauty cover for his X5, FWIW. When I had my X5, I just kept mine on.
