This is what I do with my car...
1)  Purchase a quality car cover.
http://www.covercraft.com/technalon%AE.htm
Even though the car is kept indoors, family member walk by with groceries.  A cover prevents scratches and keeps dirt/dust away from paint and interior ac/heat ducts.  
2) Put in a can of Sea-foam stablizer additive in fuel tank
http://www.riversmallies.com/guestrev_drichards3.html
You can purchase at NAPA or most auto parts stores.
3) Purchase a string of Christmas lights (C7 bulbs) and 15 amp timer.
Place Christmas light underneath car.  Set timer to come up 2 times a day for 3 hours.  The heat from lights burns away whatever dampness that may occur in your garage.   Be careful, it could attract mice and rodents.   Thats why, I don't place them under hood, just lying on floor of garage.  Some folks, purchase and tear open bags of Kingford Charcoal to obsorb moisture.  
Of course, a person should use jack stands.  I simply park my car on a couple  sheets of 4x8 plywood to keep tires away from moisture trapped on cold concrete.
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I mis-read the original post.  Why do I do this?  Anyone who lives near a large city in the midwest knows that the highway department puts down 1/2 inch of road salt/chemicals before every snow storm.