[brianogilvie]

Information that is not something you can do (such as the make, model, and registration of the vehicle) might go in the project note field, or you might keep it in another application. (I tend to keep this kind of information in a Secure Note in my Keychain.)

Something that needs to be done should probably be an action within the project: a different action for each task and each vehicle. For example, in my recurring tasks project, I have an entry for "Have Mazda Protegé inspected," with a start date of 1 August 2008, a due date of 31 August 2008, and a repeat interval of 1 year from assigned date. I have a similar entry for my family's other car. I'll enter actions for service. I don't bother putting insurance and tax actions in the project because I pay those when the bills arrive. (If my town and insurance company were unreliable in sending out bills, I would put reminders in OmniFocus.)

The basic idea is that any distinct task should be an action within your project. Some people might make "Have car inspected" into a project, with individual actions such as "Call garage to schedule inspection appointment" and "Take car to garage for inspection," but that is too granular for my taste!