from Goss’ Garage by Pat Goss

All fuel tanks have water in them, but that water isn’t from the service station. Since the latter part of the dark ages it has been a commonly held myth that water only gets into cars from service stations. Although possible it definitely isn’t typical. When you get water from a service station the quantities are usually large causing the car to quit almost immediately and not restart until the tank is drained. Actually water in fuel tanks builds up naturally over time.

Unless you’re very strange I doubt you think about how this happens but every time you remove your fuel fill cap outside air enters the tank which always contains moisture. Higher humidity means more moisture in the air entering the tank. This is also true of the air the tank breathes-in with changes in temperature. Some of that humidity condenses and slowly builds up in the bottom of your tank.

You can’t see inside your fuel tank so out of sight usually means out of mind. That is, until something bad happens like clogged fuel injectors, a failed fuel pump or even a frozen fuel line on an icy-cold morning. All are common problems and except for frozen fuel lines, seldom associated with water in the tank. Fortunately, prevention is easy; use fuel system drier (often called dry gas or gas line anti freeze) which prevents excessive moisture build up. It’s readily available under a variety of brand names.

All automotive fuel system treatments for water control are made of either methyl or isopropyl alcohol. Although harder to find isopropyl is what you want so shop till you find isopropyl because the two products deal with water and gasoline very differently.

When you use a methyl alcohol based product it soaks up water and prevents freezing. The problem is although the water and alcohol mix that mixture won’t combine with the gas so it stays in the tank causing long-term damage. Things like early failure of fuel gauge senders and fuel pumps, tank de-plating and corrosion of in-tank components. As these parts corrode they shed tiny flecks of metal and plastic so small they pass right through the fuel filter. Once past the filter they can devastate other parts, like injectors. To actually protect fuel system parts the water and alcohol have to get out of the tank.

Like methyl alcohol products isopropyl alcohol dry gas combines with water but it also causes the water, alcohol and gasoline to blend together. Once mixed together the water and alcohol move harmlessly through the fuel system as a blend with the gasoline and are burned in the engine. Isopropyl prevents moisture buildup and eliminates fuel system damage.

But be aware that not all isopropyl products are created equal. I prefer BG Products Fuel System Drier because of its consistently high quality. For you cheapskates no, you can’t use isopropyl rubbing alcohol, it’s already water saturated so it can’t absorb a single drop more water and therefore won’t help your car — at all. Plus I’ve encountered generically named products that were almost certainly just repackaged rubbing alcohol sold at four or five times the price.

By using quality isopropyl based dry gas once every month, twelve months a year, the damage caused by water in your fuel tank will be avoided.