I don't want my parents to use my car.
Why don't you want your parents to use your car?
I'm sure they will use the car to smoke crack.
It's okay to worry about and protect what you own. If you think your parents will disrespect your car, explain to them that it is off limits.
I worked hard to buy that car.
It sounds like you have a good reason not to let them use your car that you worked so hard for.