Car won't start in the cold?

Two things happen at once. The battery's chemical reaction slows, so it can deliver less current, and the engine oil thickens, so the starter needs more of it (Batteries Plus, Yuasa). That's what the cold-cranking amps (CCA) number on a battery measures: the amps it can deliver for 30 seconds at 0°F while staying above 7.2 volts (Yuasa Battery). Every model on our vehicle pages lists the CCA range O'Reilly's catalog shows for it.

Oklahoma City averages about 72 nights a year at or below freezing, and real cold comes in snaps. NOAA's daily records for the city (NOWData) show the all-time low of −17°F on Feb. 12, 1899 — and the second-coldest reading ever, −14°F, on Feb. 16, 2021, a day after it hit −6°F. Since 2000 the city has also dropped below zero in 2011 (−5°F) and 2017 (−3°F).

A healthy battery is built for this. A tired one isn't — and summer is usually what tired it out: Consumer Reports says heat is tougher on batteries than cold, and the cold is just when the damage shows. More on that in how long batteries last in Oklahoma.

1. Turn off the headlights, heater, radio and anything plugged in, so every amp goes to the starter.
2. Try to start it. If it only clicks or cranks slowly, stop and give it a few minutes before the next try (Interstate Batteries' advice when a jump doesn't take right away).
3. Look at the battery before you jump it. If the case is bulging, cracked or smells like rotten eggs, don't jump it — and never charge or jump a frozen battery (Batteries Plus, Interstate).
4. Jump it the safe way (Interstate Batteries): take off rings and bracelets and wear glasses and gloves. Red clamps first — the good car's positive post, then the dead car's. One black clamp on the good car's negative post, and the last black clamp on bare metal on the dead car, like a bracket — not the dead battery. Start the good car first. To finish, take the black clamps off first (the dead car's first), then the red ones, and don't let them touch.
5. Know that a jump only gets you going — it doesn't recharge the battery. Get it tested, or have it replaced before tomorrow morning does this again.

Stuck? Same-day service usually has us at your car in 30–60 minutes, 9 AM to 9 PM, seven days a week — and the cold doesn't change the price. Not sure it's the battery? Read dead battery or bad alternator.

Yes, if it's run down. A fully charged battery won't freeze until about −76°F, but a partially charged one can start to freeze at 32°F, the same as water (Batteries Plus). That's one more reason a weak battery is the one that fails on the coldest night — and why a frozen one should never be jumped or charged.

• Get it tested in the fall. Interstate Batteries calls winter and summer the hardest seasons on batteries and suggests testing before each; O'Reilly runs tests at no charge.
• Keep it charged: drive 20 minutes or more at a time when you can, and use a maintainer if the car sits more than a week (Consumer Reports). Idling doesn't do much — Interstate says the engine has to be above about 1,000 rpm for the alternator to charge at all.
• Buy the CCA your car calls for. Yuasa says to follow the carmaker's recommendation, and that a higher CCA can help in hard cold.
• If it's over three years old and slow on cold mornings, replace it on your schedule — here's what that costs in OKC.