Most people realize that all of us burn gasohol—a mixture of gasoline and alcohol—in our cars. Just about every gallon of gas pumped today contains as much as 10 percent domestically produced ethanol. Gummed-up fuel systems, damaged tanks and
Most people realize that all of us burn gasohol—a mixture of gasoline and alcohol—in our cars. Just about every gallon of gas pumped today contains as much as 10 percent domestically produced ethanol. Gummed-up fuel systems, damaged tanks and phase separation caused by stray moisture infiltrating fuel systems have plagued many consumers since this mixture debuted, and the problems will only get worse if government policy to increase the proportion of ethanol to gasoline is implemented. Don't get me wrong: Gasoline diluted with ethanol is a perfectly acceptable motor fuel when it's stored properly, dispensed promptly and burned in vehicles and power equipment designed to handle it. Which, unfortunately, is not always the case.
Moonshine It's Not
That 90:10 mixture of gasoline and alcohol is referred to as E10, while a different blend of 15 percent gas and 85 percent alcohol is sold regionally as E85. On this scale, straight petroleum-based gasoline is referred to as E0. Most gasoline dispensed from pumps in this country is as much as 10 percent ethanol, distilled from corn grown in the Midwest. This alcoholic cocktail was originally mandated by the EPA as a replacement for MTBE (methyl tertiary butyl ether), an oxygen-bearing petroleum-sourced chemical that was added to pump gasoline starting in 1979 to reduce carbon monoxide emissions in some regions that had problems meeting government air-quality standards. The oxygen in the MTBE (and ethanol) molecules can substantially reduce CO emissions in vehicles without modern closed-loop fuel-injection systems, which were introduced starting in the '80s.
Soon after, MTBE started turning up in groundwater, affecting the taste and smell of drinking water, so ethanol was substituted. (Shockingly, MTBE isn't considered toxic or even carcinogenic in the concentrations found in groundwater, but still.)
However: If the beneficial effects of oxygenated fuel have largely been bypassed by modern feedback-loop injection systems, which control the air-to-fuel ratio much more closely, why is ethanol still in your fuel? Because the second President Bush made a decision to offset some of our dependence on foreign oil with domestically produced alcohol, and the Corn Belt senators agreed. Ethanol plants have mushroomed, ramping up U.S. production from 1.77 billion gallons in 2001 to 10.75 billion gallons in 2009. Politics aside, odds are near 100 percent that there's as much as 10 percent alcohol in the gasoline you're pumping into your car and that 5-gallon can you use to fuel all your other gas engines.
Keeping Water Where It Belongs
The ethanol in your gas tank is uniformly dissolved in the gasoline. Alcohol tends to absorb and hold water, and in concentrations in the tank up to about 0.6 percent, any water remains in solution, presenting no problems. (Yes, there are other problems with alcohol in the fuel system, but we'll get to them later.) How does water get into the fuel tank? It's possible that water dripped into the tank at the gas station or refueling depot, or a stray raindrop or snowflake made its way into your tank or jerrycan, but most water infiltration is from condensation. As the temperature in a tank changes, air has to be ven