I imagine that their only access is by climbing up via the tires, unless mice can jump up high? If so, perhaps you only need to coat the wheels with something.
I know this is a bit gross, but a mammals specialist friend of mine and I once came across a live trap for catching martens and genets (our local "vermin") and he put the trap out of commission in a way the owner was unlikely to detect: he pissed on it. the smell of human urine was sure to keep the animals away from the trap. I'm not suggesting this for your car! and I don't know if it works with mice. But there' s a thought re there being smells they hate. If you have a cat and can train it to rub up agains the wheels every time the car is pared, that would most certainly work! LOL
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