Winter Car Prep Guide: Tires, Battery, Fluids and Safe Driving on Ice

Tires: Tread Depth Decides Traction

Tire makers say the legal minimum tread depth in the United States is 2/32 inch (1.6 mm), the point at which wear bars become flush with the tread, according to Les Schwab and Nokian Tyres. Both companies say this minimum is far from adequate for winter driving: Nokian recommends keeping winter tires at 5/32 to 6/32 inch (about 4-5 mm) for safe snow and ice traction, noting that new winter tires typically start at 10/32 to 11/32 inch.

Les Schwab describes a simple rule of thumb: once a winter tire has worn to roughly half of its original depth, it is time to consider replacement. Nokian points to the classic penny test — insert a penny upside down into a tread groove, and if Lincoln's head is fully visible, the tire needs replacing. Michelin adds that winter tires become important in any region where temperatures regularly drop below 45°F (7°C), regardless of snowfall, because rubber compounds in all-season tires stiffen and lose grip in persistent cold.

Battery and Charging System

Cold weather cuts a battery's cranking power well before it fails outright. According to a cold-weather battery guide from Battery Tender, a fully charged battery delivers only about 65% of its rated cranking power at 32°F (0°C), and that figure drops to roughly 50% at 0°F (-18°C) — even as a cold engine demands more energy to turn over. AAA says cold weather significantly reduces a car battery's power output and efficiency, and recommends having the battery and charging system tested before winter, since a battery that starts the car fine in warm weather can fail outright once temperatures drop.

AAA's Minneapolis-area advisory adds that batteries showing any signs of trouble — slow cranking, dimming lights — should be replaced rather than waited out, since cold does not create weakness so much as expose it.

Fluids, Wipers, Lights and Corrosion

AAA's checklist calls for switching to winter-grade windshield washer fluid that contains de-icer, checking antifreeze levels, and changing engine oil to its winter viscosity grade before cold weather sets in. Worn wiper blades should be replaced, and headlights, brake lights, turn signals and hazard flashers should all be tested and cleaned.

AAA's Minneapolis magazine notes that cold air contracts inside tires, so pressure should be checked more often in winter than in warmer months. It also recommends letting a vehicle warm up briefly so thickened winter oils and lubricants can circulate properly, and washing the car regularly — including the undercarriage — to remove road salt that accelerates hidden corrosion. The same advisory suggests lifting wiper blades off the windshield using the hinge on the wiper arm before an ice storm, so they do not freeze to the glass, and avoiding force on frozen door handles, since cold makes plastic and metal fittings more brittle and prone to breaking.

Fuel, Range and Crash Risk

AAA advises keeping the fuel tank above one-quarter full throughout winter. For electric vehicles, AAA says cold weather can reduce driving range by 20% to 40% and slow charging speeds, so EV drivers should plan charging stops accordingly in freezing conditions.

AAA, citing U.S. Department of Transportation figures, said roughly 1,300 people are killed and 116,000 are injured annually in crashes on snowy or icy pavement in the United States.

A Step-by-Step Pre-Winter Checklist

1. Measure tire tread depth on all four tires; replace tires once depth nears 5/32–6/32 inch, and well before the 2/32-inch legal minimum (Nokian Tyres; Les Schwab).
2. Check tire pressure, which drops as cold air contracts inside the tire (AAA Minneapolis).
3. Have the battery and charging system tested before winter (AAA).
4. Switch to winter-grade windshield washer fluid with de-icer and verify the antifreeze level (AAA).
5. Change engine oil to its winter viscosity grade (AAA).
6. Replace worn wiper blades and test all exterior lights (AAA).
7. Wash the vehicle regularly, including the undercarriage, to remove corrosive road salt (AAA Minneapolis).
8. Keep the fuel tank above one-quarter full, and for EVs, plan for 20–40% less range and slower charging in the cold (AAA).

Driving Technique on Ice and Snow

Michelin says stopping on snow or ice can take up to ten times longer than on dry pavement, and recommends keeping a following distance of at least four seconds in winter conditions. Drivers should apply brakes gently and gradually rather than stomping the pedal, and should brake in a straight line before a turn rather than while turning, since braking mid-curve can cause wheels to lock and slide, according to Michelin.

If a vehicle begins to skid, Michelin's guidance is to release the brake pedal briefly to let the tires regain grip, then reapply pressure smoothly rather than continuing to brake hard. The company also advises staying alert for black ice on bridges and overpasses, which are shaded and lose heat faster than open roadway, and keeping both hands firmly on the steering wheel. On slippery downhill grades, Michelin recommends using a lower gear and engine braking to control speed instead of relying solely on the brake pedal, and clearing all snow and ice from windows and lights before setting off.