Today we’re looking at the question “Is Ethanol Bad For My Bike?”. This is a topic that comes up often among new riders, and veterans too! If you ride up to just about any gas station pump in the US, you’ll see a sticker noting that the gas in that pump contains ethanol. It’s all around you, but most people don’t know much about ethanol.
What is Fuel Ethanol?
Ethanol is a simple alcohol. It’s the same stuff that’s in vodka and every other alcoholic drink, and it’s made the same way. By fermenting biomass, which in this case is usually corn. The main difference is when it’s made for use in fuel, the refineries put some extra chemicals in it to make it poisonous and unfit for human consumption.
Ethanol as a fuel has a long history in America. When Henry Ford was building the first Model T engines, they were designed to run on Ethanol (like Moonshine), kerosene, or gasoline because gasoline was not commonly available everywhere in 1908. Farmers could produce ethanol cheaply & quickly, though! 
Today, around 97% of the gasoline pumped in America has ethanol in it. The exact amount varies depending on the climate, but around 10% ethanol is average in most states.
Why is it in our Gas?
Ethanol is used as an oxygenating agent in Gasoline. Before Ethanol was mandated by the US government for this purpose in the 1990’s, we used a chemical called Methyl tert-butyl ether (MTBE) from the 1980’s to the point it was totally phased out in the early 2000’s. MTBE was toxic and hard to clean up when spilled, so groundwater contamination from storage tanks became a real problem. Ethanol is a more environmentally friendly alternative that performs the same function.
While ethanol has more oxygen and octane than regular gasoline per gallon, it has less energy density. E100 (pure ethanol) has 76,100 BTU per gallon, compared to 114,000 BTU per gallon of gasoline. For an E10 blend, we get about 111,836 BTU per gallon. Basically, this means you lose about 2% of your MPG going from pure Gasoline to an E10 blend. This isn’t a huge amount. Your tires being a few PSI low will have the same effect.
We mentioned before that Ethanol is used as an oxygenating agent. Oxygenated fuels allow for more oxygen to be added to the engine — this creates a larger amount of heat energy inside each cylinder. That heat leads to a much better burn rate that is more efficient, resulting in more potential horsepower and fewer harmful emissions due to a more complete burn of the hydrocarbons (fuel) in the engine. A little boost in Horsepower is always a good thing, right? These fuels generate their power on the low to mid-range of the power curve and will give an engine a bump in the amount of torque it produces.
Why is Ethanol “Bad”?
As we mentioned earlier, your bike will see about a 2% drop in MPG when running on an E10 blend vs. pure, unoxygenated gasoline. If you want to squeeze every possible mile out of a tank of gas, this may be a problem. However, with that 2% drop in MPG comes a little bump in HP/TQ and fewer emissions.
Another down side is ethanol attracts, emulsifies, and holds water (moisture). This moisture content can lead to corrosion in your hard fuel system components. (gas tank, carburetor, fuel pump, injector internals, etc.) One way to combat this is to use a fuel stabilizer, like Sta-Bil Marine, to create a barrier between your fuel and the atmosphere. If you ride regularly, corrosion with e10 isn’t much of an issue. This is because the moisture winds up getting burned in the engine as it accumulates. If you plan to store your bike for awhile, or don’t ride a lot, this may be a problem. It’s best to either drain the fuel system completely between rides, or fill it to the brim with pure, unoxygenated gas treated with a fuel stabilizer.
Another problem with ethanol, specifically with vintage and collector motorcycles, is it will degrade old-school plain rubber hoses and seals. If your bike is newer (made past y2k), the hoses and seals are probably NBR (ntitrile) rubber, which is generally e10-e15 safe. If it’s older, and not a collector piece, you can get NBR fuel lines & o-rings at basically any auto parts store. Want peace of mind? Look into using Viton fuel system components wherever possible. Viton is E85 safe. (Nitrile vs Viton) We’re working on developing Viton Harley CV Carb seals & diaphragms, so keep an eye out for those.