I'm thinking of borrowing my friends car and returning it with an empty gas tank.
That's pretty rude, I'm sure he wouldn't like that.
I'm making him realize that his car is his responsibility. He'll be grateful.
Returning your friend's car with empty tank of gas will seem like you're taking advantage of them. When borrowing someone's car it you should always make sure that you fill it up before returning it to them. If you continue to not fill up the car they most likely will not let you use the car ever again.
That's a good point and I'll make sure to fill it up next time.
I'm glad you are so open to changing your behavior! I'm sure your friend will really appreciate you filling up his gas tank the next time you borrow his car.