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Drivetrain

Gas and Water

Written by Pat Goss

You oversee a fleet of vehicles. Do you know how many of them have water in their fuel tanks? If you said all of them, you would most likely be correct. Nearly every fuel tank has water in it, but not from anything that happened at the pump. In the past, it has been assumed that water gets into vehicle tanks from poorly maintained underground storage tanks.

Although that is possible, it definitely isn’t typical. When someone does get water from a service station, the quantities are usually large causing the car to quit in a block or two and not restart until the tank is drained. No. The real trouble develops very slowly and eventually leads to big repair bills and serious inconvenience. The real culprit is a combination of air and ethanol.

Few of us ever spend time pondering what happens when we fill our fuel tanks. Off comes the fuel cap and in goes outside air. Outside air always contains moisture, but it is really bad on hot, humid summer days. Moisture from the air condenses inside the tank and accumulates over time. But there’s more to it than just removing the filler cap because every tank has to breathe to compensate for expansion and contraction of the fuel it contains. Put all the moisture from air together with a few cool or cold days, and over time, you will have a lot of water in your tank. That is, unless you remove it.

Water in fuel is another one of those vicious out of sight out of mind things that eventually bites you! Think about it. Nobody does until something happens, and even then, the problem isn’t often mentally linked to the cause. Problems could be clogged fuel injectors, a failed fuel pump or even a frozen fuel line on a cold morning. These are all common and, except for frozen fuel lines, seldom associated with water in the tank.

The problems associated with water collecting in fuel tanks have been greatly escalated by the addition of ethanol to modern fuels. Most of the gas today is E10. The 10% ethanol in E10 absorbs and attracts water, so the amount of water in fuel tanks is increasing.

The fix is easy. Use fuel system drier (often called dry gas or gas line antifreeze) on a regular basis. Regular means one 12-ounce bottle in every vehicle once every month, 12 months a year. It is available everywhere under a variety of brand names, but watch out because not all are created equal.

All fuel system water treatments are made of alcohol, some from methyl alcohol and some from isopropyl alcohol. The product you want is made from isopropyl alcohol, which is sometimes harder to find. However, it is critical to shop until you find it as there is a huge difference in the way the two alcohols deal with water and gasoline.

This can be a big problem because about the only thing the two products have in common is that they will both prevent fuel line freezing. Products made from methanol mix with the water, which sits in the bottom of the tank. When the water and methanol mix, the methanol acts just like antifreeze in the car’s radiator and keeps the water from freezing. “Sounds good,” you say, and you would be slightly right.

Because water is heavier than gas, it stays in the bottom of the tank. Not so good. In order to protect the fuel tank and the parts inside it, the water and alcohol have to get out of the tank, and that has to happen harmlessly. With methyl alcohol, the water-alcohol mixture mostly stays in the tank. Once the water and alcohol have combined, the water won’t freeze, but because it stays in the tank, extensive long-term damage can occur.

You may experience problems with parts such as fuel gauge senders and fuel pumps, not to mention rusted-out fuel tanks. Even if the tank doesn’t rust through, the water-alcohol mix sitting in the bottom of your tank may cause tank de-plating and corrosion of in-tank components. As these parts corrode, they can produce solid contaminants so small they pass right through a car’s fuel filter. They lead to problems with fuel injectors once they are through the filter.

By using isopropyl alcohol dry gas, the entire scenario changes. Isopropyl combines with water the same as methyl alcohol, but it does much more. Vehicle motion causes the water, the isopropyl alcohol and the gasoline to blend together into one liquid. Mixed together, the water and alcohol move with the gas and are harmlessly burned in the combustion chambers, eliminating fuel system damage. By using isopropyl-based dry gas once every month, 12 months a year, the ravages caused by water in your gas tanks will be avoided.

Pat Goss is the resident master technician for Motorweek TV (PBS), a columnist for the Washington Post, and the host of radio and cable shows discussing vehicle maintenance. He also was a consultant to the Prince George’s County, MD Police Department on fleet maintenance, and he is the president of Goss’ Garage in Seabrook, MD. He can be reached at patgoss@goss-garage.com.