The right fuel additive mixes in with the gasoline and helps to keep the fuel from gelling or freezing, even in coldest temperatures. It helps keep the fuel line from freezing up, and it even makes the fuel more efficient. Meaning, you might save some money at the pump. What's more to know, the additive has a detergent quality, and actually cleans out your car's fuel injection system and entire fuel system. In this day and age of pollution, your additive can also reduce the amount of black smoke emitted by your car, helping keep the air a little cleaner.
As if all this wasn't enough, a fuel additive for the winter provides your car protection against rust, and gives anti-wear protection for your fuel injectors. This can make your car actually last longer.
If you're not interested in purchasing an additional product for your car, it might interest you to know that the gas stations actually sell you a different kind of gas in the winter, one that is specially designed to function well in colder temperatures. This gas is called methyl tertiary butyl ether (MTBE).
Although you can purchase this type of gas at the pump, it doesn't have all of the benefits that fuel additive does, including the detergent benefits. It does move a little quicker through your car's fuel injection system than a summer-type gasoline when subjected to freezing temperatures, so you may want to check with your favorite gas station to find out if they carry MTBE and when they start selling it.
You may still find that your car behaves a bit sluggishly, even with the winter gas or a gas additive. If this is the case, and you've taken these precautions, you may want to have your car's battery checked.