The fuel additive is everywhere. Learn about it and beware.
In the previous issue, we looked at the effects of a gasoline’s octane rating on your engine. We also noted that ethanol is used to boost that octane rating. Here, we take a look at ethanol.
Ethanol predates gasoline as a fuel for internal combustion engines; Nicolaus August Otto used the plant-based alcohol in the mid-1800s to power his early engine designs. Petroleum-based gasoline followed in the late 1800s, and it eventually became the primary automotive fuel. As early as the 1920s, ethanol was blended into gasoline to boost its knock-reducing octane rating. Use of ethanol-blended gasoline was increased during World War II to help counter gas shortages, but it was ramped down after the war.
More commonly used as a means to increase gasoline’s octane number since the 1920s, however, was tetraethyl lead. Lead has since proven to be highly toxic, so it was globally phased out of gasoline for road vehicles beginning in the 1970s, and was slowly replaced by unleaded fuel. Japan was the first country to ban leaded gasoline in 1986, and Algeria was the last to do so in 2021. Some aviation fuel still contains lead.
Something had to replace lead as an octane booster, so in 1979, oil companies began adding methyl tertiary butyl ether (MTBE) to gas. Aside from its anti-knock properties, when used in higher doses, MTBE also had the benefit of oxygenating fuel, which helped reduce emissions. Although the long-term effects of exposure to MTBE are unclear, it too was phased out after it was found to have contaminated groundwater, either through fuel leaks at gas stations or by seeping out of underground gas reservoirs.
One characteristic of ethanol that can be either beneficial or detrimental to your engine is that it is hygroscopic; it absorbs and mixes with water. This can be beneficial, since ethanol can absorb moisture in the tank, produced either through condensation, or if small quantities of water are introduced into the tank when filling up or by other means. The water is then dispersed into the gasoline, and is safely passed through the engine and out the exhaust.
However, ethanol can only absorb a limited amount of water. If that amount is exceeded, then something called phase separation occurs. Phase separation can be observed if you add water to oil in a container; the water will separate from the oil and sit at the bottom of the container. If there’s too much water in ethanol gas, phase separation will occur, but it won’t just be water sitting at the bottom of the gas tank — it will be a corrosive mixture of water and ethanol. This will effectively drop the gasoline’s octane rating, since much of the ethanol has been extracted from the gas. And once that mixture gets into the fuel lines, it will cause havoc in the fuel system. The trick to avoid this is to keep the tank full when storing a bike for extended periods; the less air there is in the tank, the less condensation will occur.
Fuel-injected motorcycles can run on E10 without any issues. However, use of gas with 15 percent ethanol (E15) will be detrimental to performance, so try to avoid it. If you have a carbureted bike, you have to take certain precautions with E10. Daily riding isn’t a problem; long periods of dormancy are. E10 deteriorates quicker than pure gasoline, so the small volume in the float bowls will go bad sooner. If the bike is to stay dormant for more than a month, drain the float bowls, keep the fuel tank filled to reduce the likelihood of water contamination, and add a fuel stabilizer to keep the gas fresher, longer.
Modern fuel system components are compatible with ethanol. Older bikes might experience deterioration of rubber and plastic fuel-system components, so either upgrade those components (fuel lines, rubberized float needles, etc.), or find a source of ethanol-free gasoline. The same applies to two strokes; ethanol is fine in newer models — KTM, for example, approves E10 in its two strokes. Older two strokes will experience the same issues mentioned above, so it’s to be avoided.
