Engine health

[TimoBoiii]

How do I fix my engine? When you're in the garage you can see the engine Icon and it's color. I assume that yellow engine icon means I should fix something since it's health is declining. However I have absolutely no clue where to check health of each part + how to fix it. Do I really need to buy the same part again and just replace it?

[Sthovin]

I always thought that number was tied to the engine strength and goes down if you are constantly overheating it, I had to repair it a few times when I had nothing but prototype parts installed from memory so I went down a level on a few to bring it back to 100% and its been fine since

[Vice]

Engine's health goes down as you overheat it during driving, you can't replace the engine until it's fully run out of health. When it does run out of health, you can replace the engine in the garage in the same way you'd change the oil. After that, the engine will be repaired to as much health as its initial car rating was when you bought it. If you got a 4 or 4.5 rating car, it'll be solidly green health, but if you bought a rating 1.5 or so car then it'll only be yellow condition and need replacing again much sooner.

Kinda weird IMO when you basically upgrade and replace every single piece of the engine itself in the course of buying and adding new parts, but hey, gotta have a money sink somewhere.

EDIT: The bought/upgraded parts do nothing to the engine's health either way, except for potentially making it far easier to overheat and draining your engine's health faster (or at all)