Now is the time to winterize your vehicle with these steps:
• Be sure to have fresh coolant in your radiator as specified in your car’s owner’s manual.
• Switch to a thinner oil during the frigid winter months.
• Inspect your battery and make sure it is keeping a charge.
• If you live where it snows, be sure to switch over to your snow tires.
• Make sure all fluids are topped off, especially windshield washer fluid.
• Inspect your windshield wipers and replace them with heavy-duty winter wipers.
Source: https://www.dmv.org/how-to-guides/winterize-car.php