The car winterization checklist, ordered by what it prevents

The ordering principle

Every winterization list contains the same twenty items, presented as equally important. They are not equally important, and treating them that way is why people do the easy half and skip the half that matters.

So this list is sorted by consequence. What happens if you do not do it, and how much does that cost? Anything that prevents a safety failure comes first. Anything that prevents a several-hundred- dollar repair comes next. Convenience comes last, and is clearly labeled as convenience.

Tier 1: the things that fail dangerously

1. Winter washer fluid, before the first freeze

This is first on the list and it is almost never first on anyone else’s. Summer washer fluid freezes in the reservoir, the lines and the jets. When it does, you have no way to clear the film of salt spray that a truck throws onto your windshield at highway speed — and dry wipers on a salted screen smear it into an opaque gray sheet rather than clearing it.

The other glass job worth doing before the freeze is the stone chip you have been ignoring: a repair kit needs the glass at 50 to 75 F, which is a September problem rather than a January one.

That is a genuine, immediate loss of forward visibility at speed, and it is the cheapest item in this entire article to prevent. Run the reservoir low in the fall and refill with a fluid rated well below your local minimums. De-icer spray and winter washer fluid do different jobs and the fluid is the one that is not optional.

2. Tires: tread depth and pressure

Two separate checks. Tread, because it is what evacuates water and bites into snow, and because several states hang their winter traction exemptions on a published minimum — Colorado publishes 3/16 in and California publishes 6/32 in for mud and snow tires, both far above the 2/32 in legal wear limit.

Pressure, because it drops with temperature and people misread the warning light as a puncture. Air contracts as it cools: a tire set correctly on a 75 F afternoon in September reads several psi lower on a 25 F morning in January, with no leak involved. Check pressures cold, monthly, against the placard on the door jamb rather than the number on the sidewall. Putting the air back is a five-minute job with an inflator in the trunk, and the warning light will not prompt you until you are 25 percent down.

If your winter involves mountain routes, this is also the moment to decide about traction devices, because buying them at the bottom of a pass is expensive and buying them in a hurry means buying the wrong size. The rules on when chains are required are worth reading in October.

3. Wiper blades and the parked-wiper habit

Blades degrade over a summer of UV and heat, and the failure shows up the first time you need them against slush. Replace them if they chatter, streak or skip. Whether you need dedicated winter blades has a more nuanced answer than the packaging suggests.

The free habit matters as much as the purchase: do not leave wipers parked against the glass overnight in freezing weather if you can help it, and never run them to break ice free. Both tear the rubber edge, and a torn blade is a smearing blade.

Tier 2: the things that get expensive

4. The battery, and a maintainer if the car sits

Cold does two things at once, and the combination is what strands people. The battery’s available power falls — CTEK publishes roughly 35% lost at 32 F and 60% at 0 F — while the oil thickens and the engine becomes harder to turn. Less available power, more required power, on the same morning.

Which maintainer to buy comes down mostly to whether the maker publishes a cold operating range, and why batteries die in the cold explains what the device is actually preventing.

5. Floor mats, before the salt gets into the carpet

The least glamorous item here and one of the most expensive to skip. Salt solution comes into the footwell on your boots, soaks into the carpet padding, and sits against the floor pan for weeks. Padding is designed to absorb, which in this context means it holds brine against bare metal in a place nobody inspects.

A set of all-weather mats or liners keeps that in a tray you tip out. It has to be done before the salt arrives, because once the padding is soaked the mats are protecting a floor that is already wet. The mat roundup is here, and it is genuinely a rust-prevention purchase rather than a cleanliness one.

6. Underbody and paint protection, if you are going to do it at all

A sealant or wax applied in the fall gives the paint a sacrificial layer against salt spray for the months when washing is least appealing. Which product to use matters less than the timing: it has to go on while it is still warm enough to cure, which in most of the country means September or October.

The underbody is the expensive half and the one people skip. Rinsing the underside on mild days through the winter does more than any single autumn application, and it is free. If you do want to treat the underbody as well, pick the undercoating spray by the metal you are covering, and check the maker’s published application temperature before you plan the day.

Tier 3: worth doing, but be honest that it is convenience

A windshield cover saves a few minutes on every frosted morning and stops the wipers freezing to the glass. It is a genuine quality-of-life item and a small one financially; we did the arithmetic on it rather than asserting it.

A snow brush that actually reaches your roof. On a tall vehicle this crosses back into Tier 1, because roof snow leaving at speed is a hazard to the car behind and slides onto your own glass under braking. Reach is the whole specification.

An emergency kit in the trunk. Low probability, high consequence. The checklist version is here and the National Weather Service’s winter safety guidance is worth reading once, particularly the part about staying with the vehicle.

A car cover, sometimes. This one is genuinely conditional and we would rather say so: a cover helps a stored car and can harm a daily driver, because a cover put on over grit and taken off wet does more damage than the weather would have.

The one-hour version

If you have a single Saturday morning in October and want the maximum return: swap the washer fluid, check tread and pressures, fit the floor mats, and put the maintainer on the car that sits. That is under an hour, it is a small amount of money, and it covers the two safety failures and the two expensive ones. Everything else on this page can wait for the following weekend without anything going wrong.