[maple_leaf_eh]

I have had good luck with a couple of methods.

1) fill the fuel tanks with fresh pump gasoline and add a whole bottle (500 ml or such) of fuel stabilizer. Both the main tank and any jerry cans.

2) remove all non vehicle items I've been tempted to lay on the seats, the floors, the roof, or the hood of the vehicles. Then I will drape with a single layer tarp. My shelter like Rob's has no heating or cooling. My concern is moisture condensing on the cold metal. There was a warm damp wind one spring and although the top 2" of snow was suddenly soft, all exposed metal instantly got a sweat layer of droplets. I can't do much about the air coming in from below, but anything to reduce the moist air "raining" inside the shelter the better.

3) I have a solid floor of recycled plastic election signs under everything in my shelter. That reduces moisture coming up from the dirt floor.

4) The other thing I do is raise the vehicle off their tires with jackstands. Many of the tires I've scrounged up over the years have had to scrapped because of sidewall cracks when the air pressure went. The weight of the vehicle plus air or sunlight will kill the tire. The something going into a field for decades' long parking would be helped by raising the axles well above the level of the dirt on blocks, wooden pallets, stacks of scrap car tires and wheels, etc.

5) Finally, last year I tried to keep a small battery tender charger on. It seemed to work better than other times. A day or two of current circulating through the battery once a month reminds the chemistry that it is still alive.