A Winter Checklist for Your Car

Tire pressure drops by roughly 1 psi for every 10°F the temperature falls. A tire set to 35 psi on a 70°F afternoon in October can read around 30 psi on a 20°F morning in January, which is often enough to switch on the low-pressure warning. That one number explains a lot of winter car trouble: the cold changes things that were fine a month earlier. The checklist below is arranged by when each job makes sense, so nothing has to be done all at once.

Before the first frost

Coolant level and freeze protection
Battery load test
Wiper blades and washer fluid
Exterior lights and both defrosters
Tire choice for the season

Start with coolant, and only with the engine cold, since opening a hot cap can spray scalding fluid. The level should sit between the marks on the overflow reservoir. Level alone does not show whether the mix will protect against freezing, so ask a shop to test it, or use an inexpensive coolant tester; a 50/50 mix of coolant and water typically protects down to about -34°F. Use the coolant type the owner's manual names, since mixing types can cause problems.

Cold weather slows the chemical reaction inside a battery, so it delivers less cranking power at exactly the moment a cold, thick engine needs more. A battery that starts the car without complaint in September may not manage it after a night well below freezing. Many auto parts stores will load-test a battery at no charge, and it is worth doing once a battery is three years old or more, or if starts have sounded sluggish. Most car batteries last somewhere around three to five years, and heat over the summer often does the damage that the first cold morning reveals. Replacing a weak battery on your own schedule is cheaper and calmer than a jump start in a parking lot.

Replace wiper blades that streak or chatter, and swap summer washer fluid for a winter blend rated to well below your area's coldest temperatures, often -20°F or lower. Plain water or summer fluid can freeze in the reservoir and lines. While you are there, walk around the car with the lights on and test the front and rear defrosters. If winter tires are part of your plan, book the fitting now, before the first snow sends everyone else to the tire shop at once.

One piece of old advice can be dropped: there is no need to change to a different oil for winter. Modern multigrade oils, such as 0W-20 or 5W-30, are designed to flow at cold starts and to protect at operating temperature, and the owner's manual specifies one grade for use all year.

The first cold week

Recheck tire pressure on a cold morning
Clear all snow and ice before driving, including the roof
Keep the fuel tank at least half full
Pack the emergency kit

Check tire pressure first thing in the morning, before driving, against the figure on the sticker inside the driver's door jamb, not the maximum printed on the tire. Pressure read after a drive will look higher than it really is. Expect to add air a few times as the season settles in. If the low-pressure warning comes on during a cold snap, treat it as accurate: the tires really are low, and the light should go out after you add air and drive a short distance. If it comes back within a day or two, have the tire checked for a slow leak.

When snow falls, clear every window, the mirrors, the lights and the roof. Snow left on the roof can slide over the windshield when you brake or blow off onto the car behind, and some states can fine drivers for it. Modern fuel-injected engines need only about 30 seconds of idling before you drive off gently; the engine warms up faster under light load than parked.

A half tank gives you a margin if a storm closes a road and traffic stops for hours. For the kit itself, see the separate article on what to keep in your car.

Before any long winter drive

Check the forecast and road conditions for the whole route
Fill the tank and charge your phone
Top up washer fluid
Tell someone your route and expected arrival time

Most states run a 511 phone line or website with road closures, chain requirements and plow updates; check it for every state you will pass through, not just the start and end. Washer fluid disappears fast on salted highways, so top it up and carry a spare jug. Scrape the headlights and taillights clean at every stop, since a film of salt dims them more than most drivers notice. If conditions look poor, leaving a few hours later or a day later is usually the better trip.

If you do get stuck, stay with the car, since it is easier for rescuers to find than a person on foot. Before running the engine for heat, clear snow away from the tailpipe. A blocked exhaust can push carbon monoxide into the cabin, which is why the CDC's winter weather guidance recommends running the engine in short spells, about 10 minutes each hour, with a downwind window open slightly.