Obviously, your son has to have money to do the things that he is doing. If he is paying his own way to do the things that he is doing and he is not breaking any family or house rules, then there isn't much that you can do to prevent him from catering to his girlfriend. He'll have to live and learn. You mentioned that your gas bill was $691 last month, at your cost. Tell your son that he must pay his own way for "pleasure cruising". Some children will push as far as they can, because they can, until you put on the brakes!! Be firm. Stand your ground. Tell him you love him, but that his behavior is unacceptable. Once he sees that you are serious and that you are not budging, you should see a difference in his behavior. Don't give in - that is what he wants you to do.