Are you one of those optimistic drivers who doesn't worry about stopping for gas until the gas gauge needle is approaching 'E'? In cold weather that's inviting trouble, says the Car Care Council. Condensation of moisture in the air in the gas tank causes an accumulation of water. Because water is heavier than gasoline, it settles to the bottom of the tank, entering the gas line and eventually working its way to the lowest point in the fuel system.
Once the moisture freezes, the fuel flow is blocked and the engine may not start on a cold morning.
Most brands of gasoline are formulated to prevent freezing, says the Council. Additional protection in the form of gas line antifreeze, however, can prevent starting trouble in severe cold. This methanol (methyl-alcohol) based product, found among automotive chemicals on most auto supply shelves, mixes with water to prevent freezing. The solution of gasoline, alcohol and water is burned in the engine's combustion process.
Some premium brands of fuel antifreeze products contain isopropanol, capable of absorbing five times its weight in water.
Consider other reasons for not allowing the gas tank to drop too far below half full.
First, and most obvious, is the possibility of running out of gas in an area where no service stations are available.
The other reason, less obvious, applies to fuel injected vehicles on which the fuel pump is located inside the gas tank. Cooled by the gasoline that surrounds it, the pump can be damaged from overheating when the fuel level is too low.
It costs no more to keep a tank at least half full, and the addition of fuel line antifreeze is a small price to pay for the added protection it affords.
Beyond this, because a battery loses some of its output in cold weather, be certain it's OK for another winter's use. Finally, concludes the Council, make sure your engine has adequate antifreeze/coolant protection and that the spark plugs and ignition system components are up to the cold weather challenge - it'll save you down the road.