STA-BIL makes very good additives. Several to choose from depending on fuel types, ethanol etc... Also if you use a battery trickler remove the battery from the car, put in a well ventilated area. Besides just starting the car, If up on jack stands, you can work the steering wheel back and forth, if automatic place in neutral to allow the fluid to flow through the transmission. Put it in drive to lubricate the trans output shaft seal. U-joint bearings, gears. Apply brakes off and on to keep wheel cylinders and disc pistons flexible and conditioned. If on the ground try to drive it a little and turn air conditioner on for a while and the heater. Etc... What you are trying to do that you don't do just by starting the engine is to lubricate and bearings and seals that are normally lubricated by regular driving. Other wise you will get leaks and drips in the spring when you take her out of storage. Waxing the car before covering with a high quality dust cover. and many more things. great time to recheck all fluid levels, air pressure, before you put her to sleep.