One of mine loves my the Z4 best, the other will not go near any car, though he does like to sleep under it when it warm. They all seem to avoid the 350z and the TT, think the Z has the best bonnet /hood for sleeping on.
The best way is get a water pistol, but do not do it when it is on the car, if you scare it, out come the claws and it wheel spins off the bonnet, not good.

If you see it prowling after you get home wait until he saunters over and give it a quick blast, ideally near it, not a direct hit, when it gets too near, they are quite intelligent creatures, so after a few times they will start to steer clear. A bit of water never hurt them, however i agree with Lucy anything more then that’s not nice.
I am lucky nearly all of our street has cats, so we are all use to it. I rarely chase mine away as I would rather he sat on mine than damaged a neighbours car. Wish the people with kids in our street where as responsible, throwing sticks and balls at the conker tree near my car, perhaps I should use a water pistol on them.