A cat is jumping up on your car. You're tired of it leaving paw prints on your car all the time. Maybe it's your cat; maybe it's someone else's. Regardless, you want to keep the cat off your car.
The problem is that static mats and other deterrents require electricity that don't do well in an outdoor environment. Cats are naturally attracted to cars because they are warm after driving them so the radiant heat from the motor on a cold day is particularly inviting to a cat to curl up on. So how do you keep the cat off it?
Keep your cat inside. Your cat can't climb on your car if your cat isn't outside. And, keeping your cat inside will prevent the possibility of your pet getting run over by a car, killed by predators, getting parasites or getting injured outdoors.
If the cat is outside, put a car cover on your car to prevent paw prints from getting on the paint.
Lay X-mats or other passive mats on the flat surfaces of your car. The bumps on the mats will discourage many cats from walking or lying down on your car.