How to protect your car from winter's salt, snow and cold

Winter doesn't damage a car all at once. It's salt working into the brake lines over a season of short trips, moisture freezing inside a door seal overnight, and a battery that was already tired before the first hard freeze. None of it announces itself the way a cracked windshield does, so by the time it's obvious, it has usually been building for weeks. A handful of habits, most of them quick, are what keep salt, snow and hard cold from turning into a repair bill.

What winter is actually doing to the car

Three things do most of the damage, and none of them look like much in the moment.

Road salt is the one that costs money. It holds moisture and acts as a corrosive agent, and the rust it speeds up can weaken structural parts, brake lines and the suspension, underneath the car where it's easy to miss. Repairing it is usually not covered by insurance, since corrosion counts as normal wear and tear. Snow and ice matter for where they end up: snow left on the roof can slide over the windshield or onto the drivers behind, and the salty slush the tires throw up splashes onto the underside. Cold temperatures freeze the moisture trapped in the rubber door seals, which can stick a door shut, and they put real strain on a battery, especially one already close to the end of its life.

Six habits that hold the damage off

None of these take long on their own. It's skipping one, usually the wash or the battery check, that turns into the expensive kind of winter.

1. Wash off the salt, especially underneath

   Salt does its worst work where you can't see it. AAA's advice is to wash the car every two weeks during winter, and more often after a heavy snowfall or a drive on heavily salted roads, with the undercarriage as the priority. Consumer Reports puts it at a monthly minimum during snow season, more if the car is coated in salt, and calls the underbody spray a worthwhile upgrade even when it costs extra.

   A touchless wash that cleans the whole car, undercarriage included, is Consumer Reports' pick. It reaches underneath, where the salt collects.

   TipRinse the loose salt off before you wash. AAA says it protects the paint.

2. Add a layer of wax before the season gets going

   Wax creates a barrier on painted surfaces that makes it harder for salty slush to stick, per AAA, and a fresh coat before winter helps shield the paint from salt and moisture. It's not a cure: AAA is direct that wax does not prevent rust entirely, it only slows corrosion, so it's a supplement to washing and not a substitute for it.

3. Keep the door seals from freezing shut

   The rubber seals around the doors can trap moisture that freezes, which is what sticks a door shut on a cold morning. AAA Club Alliance's fix is a thin layer of glycerin-based moisturizer on the seal, which keeps it from sticking to the frame and freezing shut in the first place. Do the trunk seal while you're at it, and do it before the first hard freeze, not after a door is already stuck.

4. Get the battery tested before the cold really hits

   Cold cuts a battery's output hard. AAA puts the loss at about 35% of a battery's strength at 32°F, and about 60% at 0°F, while a cold engine can need up to twice the normal current to start.

   A battery already near the end of its life, which AAA puts at three to five years on average, is the one most likely to give out on the coldest morning of the year. Have it tested before temperatures drop, not after it fails to start.

5. Clear the snow off the whole car

   Brush the snow off after a storm, roof included, rather than leaving it for the sun. AAA calls snow on the roof a serious driving hazard: it can slide onto your windshield or blow back onto the drivers behind you. Use a snow broom or a soft-bristled brush and work from the top down; a shovel will scratch the paint and glass.

   On frozen glass, use a plastic scraper, never a metal one, and never pour hot water on the windshield, which AAA warns can crack it through thermal shock. While you're working around the car, look over the gaskets, seals and wiring where salt can seep in, since salt can corrode electrical connections; AAA's advice is to replace anything that shows wear.

6. Cover it when it's parked

   A water-resistant outdoor cover takes the falling snow and ice instead of the paint while the car sits. AAA Club Alliance counts a car cover among the ways to keep freezing moisture off the doors and locks, and it keeps ice off the windshield too. It won't do anything about the salt the car picks up on the road, so it's no substitute for the wash. Put it on over a car that's clean and dry, the same as any other season.

   

Garage or driveway, cover it right

Where the car spends the winter decides which cover it needs. A garage keeps the weather off but not the dust of a busy space; a driveway or open lot adds snow, freezing rain and winter sun on top of that.