Any time you will be laying a vehicle up you should change the oil. If not you run the risk of acids in the used oil attacking the internals of your engine. It is also a good idea to use a gas stabilizer (such as StaBil, available at WalMart and elsewhere) in your tank as modern gas formulations begin to break down in as little as two weeks. Do a Google search for winter motorcycle layups, that should give you some idea of what to do in order to make sure your car is ready to go.