Keep cats off your car by using the same principal that you would use to keep cats off the kitchen counters. Know that when teaching a cat something new, that they do not get the message immediately; Be patient all cats can learn something new unless they have a disability.
Before implementing any cat deterrents to keep the cats off your car by locating the owner of the neighborhood cat. Meet with the owner and inform them that their cat is being a nuisance and ask them to keep their cat indoors. Tell them any damage (scratches) on your car that they will be responsible. Most pet owners do not want to part with their money and they will keep their cats indoors and away from your car.
Now if your problem is stray or feral cats then the best way to keep them off and away from your car is by making them uncomfortable.
Keep cats away and off your car by grossing them out. Spread a layer of orange or grapefruit peels in the same area as your car. Cats do not like citrus and this natural pest control will keep the cats off your car. This cat repellent is effective for a short period of time as the scent does wear off as the peels dry. Replenish as needed.
Another way to keep cats off and away from your car is to BUY a commercial ultrasonic pest control alarm. The high frequency alarm will go off when the motion sensor detects the cats. This pest control alarm is an effective deterrent for cats with good hearing.
There are other products that are effective in training cats to stay away from your car. Amazon and PetSmart have Scat Mats. Set a scat mat on the hood and one on the trunk of your car. When the cat attempts to jump onto the car they will land on the scat mat and will get a slight shock. The shock will alarm the cat and they will quickly jump off the car.
Some cats will try to get back up onto the car but when they feel the static shock they will jump off the car and will leave the area. The Scat Mat is an effective and quick method for training cats to keep off the car.
Know that the best way to keep cats off your car is to park it in the garage and shut the door. Of course if that is not an option you can always buy a car cover. However car covers are not fool proof because cats may mark it and then the cover will stink.
Do you have a cat problem in your yard? What deterrents, repellents do you use to keep neighborhood cats out of your yard and away from your car?