Since you probably won't get results by making a game of cleaning up the room, you will need to find something that is rewarding to the child. When a child reaches adolescence, he is able to understand the rules, even though he often won't follow them. A way of getting the room clean under these circumstances will be to explain the rules you have devised. For example, a rule could be the family car cannot be used if the room in question is not clean. It is important to understand you will be tested to see if you really mean it about the rules.
Consistency is absolutely necessary in applying the rules.
Also, let the responsibility of remembering the rules rest with the child. Don't keep reminding him the room isn't clean yet and Saturday night is almost here. Using the car isn't the important thing. Learning to be a responsible person and keeping a clean room seems to be a higher priority for your child to live a productive and responsible life. Don't think I am concerned with whether there are socks littered about the place or that your teenager should be using the family car.