Antifreeze is fairly sweet because it keeps your coolant fluid from overheating and from freezing. As with most motor repairs, make sure you're not doing this while the car is still hot (otherwise you'll end up with a face full of hot stuff, become the Joker and terrorize Gotham City).
First, open the hood to find your tank of antifreeze. The cap should say "coolant" or "radiator fluid" or something clarifying which reservoir is which. It'll also usually tell you what kind of antifreeze you want or need (pink stuff or green stuff are typically the varieties). If the level inside is below the line you may need to add more of the correct kind of antifreeze, which is something you'll probably want to do with a funnel. If the level is at a normal level then you're okay.
Most cars typically have a 50/50 mix of antifreeze and water, though you can adjust your mixture to a higher level of antifreeze (max 70/30 antifreeze/water) for colder climates where subzero temperatures are more common. Make adjustments based on the recommendation of friends and your mechanic if you're not sure what kind of mix is required for your climate. Just make sure to return your car to a 50/50 mix for the summer months.
Return to "How To Winterize Your Car In Ten Easy Steps."