Thursday, May 5, 2011

Ethanol Does Not Hurt Engines

A lot of folks seem to think ethanol will hurt their engine. This is not true. Here is how I know that:

The following is an excerpt from the “ethanol properties” downloadable document located on the ethanol projects sub-page on my website It addresses what materials can be used with ethanol and with “stiff” ethanol blends.


“Materials compatibility is the next most important item. Ethanol is known to dissolve or damage certain materials, and can cause enhanced corrosion of metals, especially bare aluminums. You have to know what these pitfalls are, in order to avoid them.

Materials that cannot be used with ethanol but can be used with gasoline are old-time lacquered cork carburetor floats, the antique zinc-based “pot metal” castings for fuel pumps and carburetors, and Lexan or Plexiglas if there is warm vapor contact.

Materials that cannot be used with either gasoline or ethanol are natural rubber, butyl rubber, and polystyrene plastics. Both fuels dissolve these materials.

Materials that can be used with both fuels include neoprene rubber (any color), steel, aluminum, most polypropylene-type plastics, and both Lexan and Plexiglass if limited to liquid contact. Aluminum should be protected by a surface coating. Update 6-9-11: Teflon is also good with both fuels. Thus the typical aircraft fuel hose (stainless steel braid over teflon) is fine with ethanol.

The corrosivity of ethanol to aluminum and steel is not serious as long as the ethanol is dry, and it is far less than that of methanol, whose corrosivity gave both alcohols a bad reputation. The presence of 2+% water content greatly enhances ethanol’s corrosivity, however. The presence of water in the fuel can also cause phase separation problems (see below). Thus, if ethanol is used neat or in blend, it should be kept very dry.

As a rule of thumb, “anything good for gasoline is good for ethanol” is a pretty good guide, as long as Lexan or Plexiglas are not involved, and no truly antique parts are used (those are the zinc-based pot metal castings and the lacquered cork floats).”


To this I would add the following about the “scare stories” being circulated by the small engine and boat motor lobbies. They quite often claim that gasohol fuels cause damage requiring engine overhaul. This is simply NOT TRUE. But there are two troubles to anticipate and avoid:

First: dirty fuel systems, which can be traced to really poor housekeeping on the part of the owner. The presence of ethanol in the fuel, with its solvent properties, will mobilize any pre-existing dirt in the fuel system, something gasoline will not do. This is quite the common problem with lawnmowers. That mobilized dirt will clog either a fuel filter or a carburetor jet, or both. You simply drain out and replace the dirty fuel (including that in the carburetor bowl), and clean or replace the clogged item. You DO NOT need to overhaul the engine.

Second: pre-existing water in the fuel system, something quite common in boats, and in lawnmowers kept outside in the weather. Ethanol in the fuel will scavenge water bottoms up to an unpredictable point (5-25% water by volume). Beyond that “limit”, the fuel will “phase separate” into a wet ethanol layer underneath a dry hydrocarbon layer. The engine is not carbureted to run on straight ethanol, and so will not run on the wet ethanol layer. Neither will it run successfully on the dry hydrocarbon fraction, which is devoid of any octane boosting ethanol or methanol added at the refinery. Simply drain and replace the fuel, including that in the carburetor bowl. You DO NOT need to overhaul the engine.


If your fuel system is clean and dry, you may add any gasohol blend to an unmodified four-stroke engine as a “drop-in” fuel, up to about 35% ethanol, no modifications required at all. It will get the same fuel consumption it got on gasoline, it will run cleaner internally, its oil will stay clean longer, and so the engine will actually last longer. It will soot less out the exhaust, too, which means it is causing less pollution (US EPA’s oil lobby-induced fears notwithstanding).

I have been using E-22 to E-35 blends in unmodified cars and four-stroke lawn equipment for 5 years now (Brazil has been using E-22 since 1980). These vehicle and equipment items range from vintage 1960 to vintage 1998. I have been using straight E-85 in an old car (vintage 1973) and a really old farm tractor (vintage 1944) just as long. If there was a problem with ethanol, I would know about it by now.

There is no problem!


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