Today, we take another look at ethanol for our weekly Greenlings post. You've probably noticed that many vehicles are labeled with a Flex Fuel badge from the manufacturer, indicating that the car or truck is capable of running safely on E85 – a blend of 85-percent ethanol and 15-percent gasoline.

For this article, we're not talking about E85 or other mixtures with high concentrations of the alcohol fuel. Even regular-grade gas that you get from the fuel pump nearest you is very likely to have at least some amount of ethanol added, and in fact, the single largest single use of ethanol in the world is as fuel. Why? And does your car need any modifications to use this ethanol-infused gasoline? Read on to find out.


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Lead Photo by drewzhrodague. Licensed under Creative Commons 2.0


In the early 1990s, the United States government issued a series of amendments to the Clean Air Act that included the requirement to use oxygenated gasoline (minimum oxygen content of 2.0-percent by weight for reformulated gasoline in ozone non-attainment areas, for what it's worth) to help the fuel burn more completely in combustion. One of the favored oxygenates was methyl tert-butyl ether, or MTBE.

This chemical compound was chosen due to its low price and because it helped mixers generate higher octane ratings. All seemed well until California discovered in 1995 that MTBE was showing up in high concentrations in drinking water, which was traced back to spilled gasoline and leaky underground containers. Ethanol was widely seen as a safer replacement for MTBE and its use was pushed by the agricultural industry here in the States.

So, now that we know why regular gasoline probably has at least some ethanol in it, the next logical question is do you need to be worried about it? The answer is a qualified no. Today's cars and trucks are all fully capable of running on E10, a blend of 10-percent ethanol and 90-percent gasoline. Sophisticated computer systems and sensors constantly monitor the engine and the exhaust to be sure that everything (i.e., the air-fuel mixture) is kept at its optimum level.

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Even older cars (say, from the mid-1980s or so) are unlikely to be damaged by low concentrations of ethanol in gasoline, though it's possible a carburetor may need to be rejetted to run on highly oxygenated fuels. Classic cars and trucks may need some replacement of older rubber lines and fittings that could potentially be damaged by high concentrations of alcohol in gasoline.

But what about the environment? Is a 10-percent ethanol blend eco-friendly? That's a tougher nut to crack. Obviously, the burning of fossil fuels isn't a great thing in and of itself for the environment, so the question may be whether burning ethanol-infused fuel is better or worse than straight gasoline. Since ethanol is used to oxygenate the gasoline mixture, which in turn allows the fuel to burn more completely and therefore produce cleaner emissions, its use in fuel has obvious benefits for air quality.

Of course, the full issue is a bit more complicated than that. For a more detailed discussion on the merits and drawbacks of ethanol (including cellulosic ethanol), click here.

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