It's happening, winter is upon us (queue collective groan). While it's not the end of life for car people, the majority of us hideaway in our homes until the DOT is through with salting the earth. We all have our own rituals we do when putting our toys away. Some people do the basic fuel stabilizer and a battery tender. Others do the full gambit of moth balls under the hood, dryer sheets in the interior, battery tender, fuel stabilizer, burning a smudge stick to ward off evil spirits, putting the car on jack stands, climate control in the garage, etc.
There are also some people who don't even bother prepping and just stick their car in the back of their driveway for five months. That's something I wouldn't exactly recommend though, unless you enjoy spending a small fortune in batteries and rodent removal. So what's something that's totally required and what's pure hogwash? We're going to go through the basic steps for making sure your car doesn't end up as a pile of thermite in your driveway come March. This isn't a complete list of everything you could possibly do but it's a list of top recommendations we've verified with a number of automotive technicians and shop owners.
Frankly, you really can't be too careful when putting your car away and it's usually best to do everything in your power to preserve the car. The worst thing for a car is let it sit, unused. Unfortunately, during winter, it is almost a requirement to store most cars and having no preparation at all is usually results with needing to repair a multitude of problems months later. Batteries deteriorate, fuel can "go stale," outside storage promotes rust, and a car is basically an apartment complex for rodents if left unmoved.
Prior to storage, waxing and detailing your car is a great first step. The wax will help seal the paint from moisture getting through it and will provide a defensive layer from anything that can harm paint in the dust around the garage. When detailing the interior, making sure there isn't anything in the car that can attract rodents is a key measure as well.
Once you do begin the process of storing a car, it's imparent to insure the car is left away from sources of road salt or moisture, namely streets. Outside storage breeds rust and this is mostly due to humidity and even garages with dirt floors can have moisture transfer up underneath the car. Minnesota is an extremely humid climate, that is part of why our winters feel so cold, the moisture in the air is like a growth steroid for rust. Even with a tarp over the car, the moisture caught under the car can rot it from the bottom up. I've seen no shortage of cars that looked great on the outside but underneath it looked like a colander. If you do absolutely have to store on a dirt floor, laying down a plastic tarp will help significantly.
The first priority in storing a car over the winter is finding a garage or more climate controlled area to store the car in. While some people with the means available can afford climate controlled garages, the vast majority of us will be using our normal garage behind our house or renting one out from some kind little old lady. Even the most basic garage or storage shed can provide some shelter from the elements and reduce the likelihood of parts corroding. This should always be considered over just popping the car in the corner of your back yard. Regardless of where you store your car, rodents making homes in your car is a constant issue.
For actual deterrents to rodents, there are lots of options but the most common is sticking some dryer sheets or mothballs in the car. Mothballs are significantly more effective but a dryer sheet can be used in a pinch. If you're using mothballs, placing them on top of each tire and under the hood will be best, dryer sheets will require more locations and can risk a rogue mouse getting over the smell and using it for a nest. Some peppermint oil mixed with water and sprayed on the dryer sheets and around the car will help bolster the defensive measures. I do strongly advise against traps or D-Con on the chance that the mice makes it into the car before it dies and begins to decompose.
The most glaring issue is the battery will drain itself, even if the vehicle is not left on, this is due to any electronic systems that take a passive draw of power. Things like the clock in your car, the ECU and other systems sap a small draw of power. Once a battery goes completely flat, a quick charge, like jumping the battery, can damage the plates internally on the battery.
If your battery does go flat, a slow trickle charge often can save you from a world of pain. To completely avoid this problem, most people put the car on a trickle charger, like the Eastwood Battery Tender I have pictured above. A trickle charger reads the charge of the battery and provides a slow charge once the battery drops below a certain voltage.
A common worry of many people storing cars for winter is "stale" gas. Gasoline is a complex chemical from the start, it is a fine balance between being able to combust the gas and fighting it from detonating while in the combustion chamber of a car. While gasoline should stay nearly indefinitely if stored in a properly sealed container, a gas tank on a car can allow air exposure, older cars are more likely to not be air tight than newer cars. When there is an air space in a gas tank, the more volatile components of gasoline can evaporate away and natural moisture from the atmosphere can get into the fuel.
If you are worried about your gasoline going bad over winter, a few steps can be taken. Make sure your tank is full, this will minimize the empty space in the gas tank and result in less potential atmospheric air in the tank. The next step is adding a fuel stabilizer to the gasoline. This will chemically stop any oxidization catalyst from degrading the fuel and will prevent the absorption of moisture.
While talking about the powertrain, if you have a water-cooled car, making sure your coolant is in good condition can help prevent a multitude of problems from frozen water cracking open a coolant galley, which sounds far fetched but is not unheard of, to something as minor as a plugged up heater core. A coolant flush with a proper coolant/water mix if you haven't done one recently is a good idea. Too much water in the mixture will allow it to freeze and too little water causes the mixture to be corrosive.
Some people worry about flat spots on the tires, usually making they're properly aired up will save you from this issue. If you're really worried about this, putting the car up on jackstands can help but, personally, I just air up my tires a bit more than usual and I've never had a problem. If you find your tires flat or really low after winter, it is a leak on the tire which is more of a matter of maintenance than storage and should be addressed. Another point of consideration while we have our minds on what's in your wheel wells would be preventing rust on the brake rotors. Usually surface rust is managable if your garage isn't too humid but if you feel it is necessary, a thin layer of WD-40 or other water displacing sprays can prevent premature wear on your rotors. This is more important if you're storing your car in a humid area.
There are a number of other things you can do and when storing a car, it's really up to you to decide what level of preparation you want to go through for winter. I've seen people literally put their car in an air tight, climate controlled, plastic bubble before, so anything is possible. The main goal when preparing to store your car for winter is to be able to pull it out, hop in after a few months and drive it on the first salt-free day of Spring completely trouble free.