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Ethanol in Fuel - Problems & Causes

Wondering what you need to know about ethanol in gasoline? Here you can find simple and understandable information on what ethanol blends do and the problems they cause.


Ethanol blends have been used for years as “oxygenate” additives to gasoline to reduce vehicle emissions and lower harmful urban air pollution.  This practice is mandated by clauses in the Clean Air Act of 1990, which established new guidelines dictating the production of reformulated gasoline fuels.  These new fuels would burn more cleanly as a result of their formulas being modified to include things like ethanol.  Ethanol, methanol, and MTBE proved to be the most common and feasible oxygenates for widespread use.  These additions are called oxygenates because they add more oxygen to the gasoline blend – more oxygen in the fuel produces lower levels of harmful pollutants after the fuel is burned.

Finding ethanol and ethanol-free gasoline

Since about 2006, gas stations have been putting up pump stickers saying "this fuel may contain up to 10% ethanol".  You used to be able to find a station that would sell "pure gasoline" without ethanol, but those days are coming to an end.  Tracking web site like the popular puregas.org show less than 5,000 stations left across the US and Canada that sell pure gasoline.  This is a very small number out of more than 100,000 total stations.

E15 Replacing E10

What's more, the days of only 10% ethanol (E10) are coming to an end too, as Congress approved the manadatory increase in ethanol concentration up to 15%, starting in October 2010.  As with many thing, the actual implementation of this increase has taken a lot longer than the original plan dictated.  Many analysts are expecting E15 to be available in most gas stations across the country later in 2012.

All of this wouldn't be a concern for drivers if ethanol didn't cause serious problems in their vehicles and equipment.  Following is a rundown of the major effects ethanol has on cars and trucks.  These problems are also applicable to boats and small equipment as well.

Loss of Mileage

Ethanol contains less chemical energy than gasoline does, and this means less mileage for the driver.  This is because ethanol is a smaller molecule with fewer carbons in its structure (and more oxygen).  More carbon means more energy and, conversely, less carbon in ethanol means less total energy when burned.

3-5% drops in mileage for E10-E15 are common, even higher for higher ethanol concentrations (though only specially modified vehicles can run on really high ethanol concentrations like E85).

Ethanol Damage

Ethanol eats away at rubber and plastic parts, dissolving them over time and leaving you, at best, with performance issues, and at worst, with expensive repair bills. The dissolved plastics and resins now in the fuel have to go somewhere, and that typically means either plugged fuel filters or a nice buildup of gummy dark deposits in injectors and on valve stems.  Vehicle and equipment performance goes out the window at this point.

Fleet managers using ethanol have to be keenly aware of this solvency issue. So too must consumers who are used to putting regular gasoline in their lawn mowers and older equipment. Some of this equipment is stored for long period of time, and when the equipment won’t start again, it's found that the ethanol has dissolved and damaged the older rubber and plastic parts.

With respect to E15, the research has found that cars and trucks made after 2001 tend to be made with materials in their fuel systems that are more resistant to ethanol damage.  Vehicles older than this are still susceptible to the above effect.  Unfortunately this does not hold true in general for boats and small equipment.

Consumers who put ethanol-gasoline in their small equipment in the past year found out the bad news about ethanol solvency, with their mowers, lawn equipment and other small equipment suddenly becoming inoperable due to fuel lines and seals and other fuel system components being damaged by the ethanol solvency.

The impending transition to a 15% ethanol content from 10% should mean these problems are amplified in the marketplace.

Water in Fuel and The Problems It Causes

Ethanol is really good at pulling water out of the air around it. This is simply a characteristic of its nature that cannot be avoided.  Manufacturers who produce pure ethanol for chemical laboratories can’t sell 100% pure ethanol because there’s always a little bit of water in it.

As the water is absorbed by the ethanol-gasoline blend, it will be absorbed into the fuel.  Every ethanol blend has a point where the amount of water absorption cause the ethanol to break out of suspension. The water condenses in the fuel tank or storage tank and will pull the ethanol out of suspension with the gasoline in a process called Phase Separation. This is bad news because the fallout strips the octane out of the gasoline, leaving you with a layer of octane-poor gasoline on top and a water-ethanol layer mixture on the bottom.  If the water-alcohol gets sucked into the combustion chamber, you have the potential for real engine damage.  At the best, you'll notice a big difference in how the engine is running.

Ethanol Sludge

Another phenomenon seen in the marketplace is an unintended consequence of the implementation of ethanol blends into a fuel supply formerly containing MTBE.  MTBE was the oxygenate of choice across the country in the early and mid 90 to comply with the Clean Air regulations.  However it was phased out after studies found it contaminated groundwater supplies (it made them taste really bad). It was then that ethanol took MTBE’s place.

Many states have phased MTBE completely out of their fuel supplies, but there are some states (including Florida) where you can still find MTBE present of “pure gas” supplies.  This is most commonly found in gas supplies intended of “off-road” use – such as in boats. 

The unintended consequence part of all this is that when you introduce E10 or E15 ethanol-blend gas into a fuel tank or system that may contain ethanol-free gas with MTBE, the ethanol and MTBE chemicals react together and form a nasty brown sludge.  This sludge, as you may expect, can cause big issues in your engine.   


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