Whether for winter in the northern climes or just for an extended period of non-use, you may, from time to time need to put up your car for storage for a few months. There are a few things you need to take care of if you expect it to work the same way as it did when you parked it.
I'll mention the emergency (hanbrake, e-brake) first simply because my mechanic yelled at me today for leaving it on in a car that's supposed to be now resting for winter. If it's going to not work in spring, you're much better off if it doesn't work in the OFF position rather than in the ON position. They have been known to seize, in fact there are some that say they always do. The truth undoubetly lies somewhere inbetween, but the fact remains: it's prudent to leave the handbrake off during long term storage.
Tires can get flat spots on them if they sit too long in one position, so you have two choices here: you can move the car from time to time if that is practical or use jackstands. If you decide to move it, once every two weeks ought to do it, about 6 inches at a time. Or, you can can put the car on jackstands. If you do this you don't really want the jacks bearing the full weight of the car as you don't want to store the suspension in the loaded state, rather, you want to take enough weight off the wheels and tires so they aren't bearing too much of the weight, but not enough that the tires are off the ground. This way you won't have to move the car during storage (but it's a but more work getting it up on jackstands). Put as much air in the tires as they can take. The Porsche guys say 45 psi regardless...
Put a greasy rag in the tailpipe(s) to keep things known (moisture) and unknown (mice?) out. Don't forget to take the rag out before you ever crank it over.
A properly charges battery is good to -80F so you don't really need to remove it. Just disconnect it and make sure it's fully charged. Here's the catch though: if you have electronics that needs a steady suppy of electricty you're going to have to keep the battery charged at all times, trickle charging it from time to time to compensate for the low current drain from things such as radios. The Becker 754 as found in cars in the 1986-1987 timeframe will need to be reset by the dealer ($$$) if it's internal battery loses it's charge; later radios are merely coded. In the early 80's a lot of people swiped Mercedes radios and this was MB's first cut at an anti theft radio. Amazingly, the company survived.
The air conditioning system should be run every two weeks to keep the seals fresh. Failure to do this can result in a loss of compresssor efficiency. I'm not sure exactly you're supposed to make the compressor kick in in the middle of February but hey, I live in Canada and only need the A/C on the second tuesday in August so who cares? You'll figure it out.
Some people recommend leaving the doors and trunk open. This is a good idea as it lets the interior breathe and prevents mildew. But, this really only works if your car is in a nearly hermetically sealed chamber. In the real world mice and other vermin can wreck havoc in your car. I'd be more tempted to keep the windows ever so slightly ajar, and make sure there's lots of cats around..
The car should be as clean as it can so this means washing it but not on the day you're going to put it away. You want to wash it a few days ahead of time to give it a chance to dry thoroughly from all the little nooks and crannies that accumulate moisture.
Vacuum the interior. Condition the leather with Leatherique. Put a light coat of Vaseline on door seals and the trunk seals for protection.
Change all the fluids and filters. There's just no point in letting a car sit with dirty or cantaminated fluides in it. Change everything: oil, transmission fluid, brake fluid and coolant. You'd have needed to change them all in the spring anyway. Make sure the windshield washer reservoir is full.
If you have a plastic gas tank, drain or siphon the gas and let the engine run until it runs out of gas. If the tank is metal, draining all the gas might result in rusting of the tank. In that case, fill the tank to prevent rusting, but be sure to add a gasoline stabilizer to prevent the gas from separating and deteriorating, which it does after 30 days.
To prevent rust on the bores, remove the spark (or glow) plugs and put about a cup of oil in each cylinder. Turn the engine over to lubricate the bores, then put the plugs back in. Don't use synthetic for this, it creeps too well, use plain old dino juice or something like Marvel Mystery Oil.
A cover shouldn't really be necessary in a closed building, but if you use one make sure it can breathe. The only place you want plastic us under your car not on top of it.
Block the windshield wipers off the window.
Push your clutch in once a month.
If you run the engine, let it get up to operating temperature. Take it for a 10 mile run if you can, the worst thing you can do for it it run it for 30 seconds or so then turn it off. You'd be better off just leaving it than doing that.
Richard Sexton, Nov. 8 2003