This story was originally published in 2008 in Ride Oklahoma and written by Chris Johnson.
Is alcohol (ethanol) in gasoline bad for your motorcycle? The answer is generally no, but you need to be aware of ethanol’s differences and quirks.
During a recent fuel stop in a remote area I got a chuckle from large signs posted on each pump shouting, “100% Fuel – No Ethonal!” The misspelling of ethanol complemented the mistaken idea that ethanol is some harmful mystery additive and not a fuel. Joe the C-Store owner not understanding the complex chemistry of transportation fuels is understandable. Few do. This article hopes to clarify a few points.
Motorcycles and gasoline are historically tightly bound. A strange liquid was found to precipitate out in natural gas pipes and thus called, ‘gas’oline. It was briefly used as a home heating fuel in Germany but banned due to too many homes burning down. The nuisance fluid then found fame by fueling Gottlieb Daimler’s 1885 wood framed motorcycle containing an 1876 Nikolas Otto invention, the ‘Otto’ or 4-cycle engine. Since then both gasoline and motorcycles have evolved together dramatically.
Traditional gasoline was a blend of hydrocarbon chains of various lengths such as the shorter heptane and longer octane. Gasoline combustion speed was a matter of proportioning more slower-burning octane to faster-burning heptane to reduce ‘knock.’ We retain the legacy concept of ‘octane rating.’ As engine performance and compression increased, further innovations in anti-knock compounds were required, like the long-running tetra-ethyl lead that led to premium being called ‘Ethyl.’ Growing concern over environmental lead contamination led to the phasing out of tetra-ethyl lead and the phasing in of Methyl tertiary-butyl ether or MTBE, a fuel and an additive. MTBE constitutes roughly one tenth the volume of gasoline. It boosts octane and chemically supplements atmospheric oxygen to promote better fuel burn. But MTBE is an environmental contaminant that likes to travel far underground from leaky fuel tanks, so it too is being phased out. A convenient replacement is at hand, ethanol, which is also a fuel, octane booster, and oxygenator.
Ethanol as a fuel has been around since the `40s, but it wasn’t until the 1980s that it acquired greater fame and utilization, being marketed as ‘Gasohol.’ It was received with a big yawn. Gasoline-MTBE was cheap and plentiful and worked just fine. Environmental and fuel supply concerns, in concert with a powerful political constituency – corn farmers, have brought ethanol to the forefront. In the Midwest, it is said, “We drink the best and burn the rest!” But like tetra-ethyl lead and MTBE, ethanol also comes with baggage. Pure ethanol is easily lost by evaporation, is a very strong solvent that is incompatible with older gaskets, rubbers, and storage tank materials, and it strips ‘passivating’ layers (stable metal oxides) from aluminum and brass, increasing the potential for electrolytic corrosion. Older motorcycles with aluminum or fiberglass/resin fuel tanks, older rubber and gasket materials can have problems with fuels containing ethanol. Ethanol scours fuel systems and suspends contaminants, leading to clogging of orifices and filters when ethanol is introduced to older fuel distribution equipment and older vehicles. The petrochemical refining and distribution industry is currently spending billions to retrofit systems for ethanol.
Perhaps the most important baggage however is ethanol’s love affair with water. Corn ethanol undergoes distillation, a process of driving all of the water out. Thereafter, ethanol remains ‘hungry’ to recombine with water. As a blend with gasoline, currently most common as E10 or 10% ethanol, the love affair with water retained. But the blend can tolerate only so much intimacy.
The graph shows how water tolerance is fuel-temperature dependant. Warmer fuel can harmlessly absorb some water, but consider how only ½ of a percent at 72 degrees is tolerated. That’s only .64 ounces per gallon or 5cc per liter! Given this problem you may begin hearing a new term, ‘phase separation.’ Phase separation is what happens when gasoline-ethanol is pushed beyond its saturation point, either by the inclusion of more water to already saturated fuel, or with a drop in fuel temperature, such as happens with the passing cold fronts during winter.
Water also phase separates out of gasoline-MTBE, but it tends to stay separate at the bottom, often harmlessly for years. With gasoline-ethanol complex chemical processes begin and apparently require only a few months to mature. With frequently-used vehicles the fuel is often refreshed, but with infrequently-used vehicles, such as recreational motorcycles, the fuel is not often refreshed.
Carbureted vehicles are more vulnerable to changes in fuel than fuel injected vehicles because float bowls are vented, allowing atmospheric water to interact with the high surface-area-to-volume float bowl fuel. If you have a carbureted motorcycle with a non-vacuum petcock, it’s a good idea before to shut off the fuel cock and run the bike out of fuel, even pulling the choke as it starts to die to remove all of the fuel. With vacuum petcocks, you can clamp off or un plug the vacuum supply to shut off the fuel.
Ihave lots of motorcycles and unfortunately can’t ride all of them at the same time. I also run a ranch and have many ranch support machines, from mowers to welder-generators. All of these vehicles must sit for extended periods. That was no problem at all until this summer, when I discovered that my primary source for fuel had changed from gasoline-MTBE to E10 the winter before. I suddenly had mowers and motorcycles not wanting to idle, and my welder-generator died during a welding job. Inspection of the mower carburetors revealed yellowish cheesy blobs in the float bowl, clogging the tiny low-speed jets. The welder-generator’s fuel-water separator bowl got repeatedly clogged with white strings of cheesy material. I drained some of the fuel into a white plastic cup and was startled by the yellowed, smelly fuel, and the amount of suspended materials.
Clearly this fuel came into contact with more water than it could tolerate, and over the ensuing months evolved into a nasty soup requiring a total fuel transfusion.
A former life lesson was ‘keep your powder dry’ to hunt and defend yourself. With ethanol fuels, ‘keep your fuel dry’ so you can go places, and if you store fuel, keep the caps tight and try not store your fuel outdoors, exposed to high humidity, rain and temperature swings.
What about fuel stabilizers? I was able to dig up only marketing claims, so I can neither recommend nor speak against them. I personally have some anecdotal evidence for unclogging partially-clogged pilot jets with carburetor and fuel injection cleaners, and products like Sea Foam, but I can’t confirm the jets didn’t just unclog with riding the bike and having the solvent properties of the fuel unclog the jets.
In this ascending age of renewable fuels, you will no doubt get exposed to some hype and ignorance. Keep in mind there is no free ride concerning fuel sources.
It takes fossil fuels to till, fertilize, harvest, transport, distill, and transport ethanol, just like it takes a power plant, often burning fossil fuels, to charge an electric car.
Regarding efficiency, there is also no free ride. Vehicle engines require a narrow range of air-fuel ratio or AFR to run optimally, neither too rich, which wastes fuel and pollutes more, nor too lean, which result in soft power and high combustion temperatures. All fuels have a volumetric energy density, which is how much work can be done with a given volume of fuel. Pure ethanol happens to be 35% less energy dense than pure gasoline. When maintaining the narrow range of AFR, producing the same power, as you increase the percentage of ethanol to gasoline, you reduce fuel economy, up to about a third for pure ethanol. Burning E10 you’ll likely notice no difference, but higher percentages of ethanol will require rejetting to maintain power and prevent your motorcycle from running too lean. You might squeak by with E20 without rejetting, but keep in mind many modern bikes are already jetted on the lean side, for emissions reasons.
I’d not run E30 without rejetting and definitely not E85, which is intended for Flex-Fuel Vehicles or FFVs which have sensors to detect high percentages of ethanol. Fuel injected motorcycles can compensate the AFR via an exhaust oxygen sensor, but likely not enough to burn E20 or higher.
The Renewable Fuel Standard is now the law of the land, setting a very ambitious goal of supplying 1/3rd of our transportation fuel needs by 2022 through ‘renewable’ fuels. Half of that goal is slated to come from conventional biofuels like corn ethanol, so ethanol is here to stay. We motorcyclists are going to have to learn about and adjust to changing fuels.