I park my M roadster for three to four months during the winter. For these extended periods I fill my tank and add Redline SI-1 Injector Cleaner, place 2amp battery charger on the system, park on foam pads and air tires to 40 psi. (Besides all the washing, waxing, vacuuming and covering the car.) For 3-4 weeks you may need only keep tires inflated, and add the battery charger.