Why is ethanol bad for motorcycles?
Before we dig into ethanol’s effect on your motorcycle, let’s go back a quick second in history. So the Environmental Protection Agency (EPA) sets biofuel blending requirements for the refining industry. Congress created the Renewable Fuel Standard (RFS) program which is basically a regulation that is aimed at supporting domestic agriculture and reducing U.S. dependence on foreign oil. There are upsides to ethanol. It is renewable, boosts the octane number of fuel and actually burns more completely and at a cooler temperature than gasoline. There are many arguments on the actual environmental benefits, but we won’t delve in that deep.
By 2007, the Energy Independence and Security Act required 36 billion US gallons of renewable fuel use by 2022. Ethanol production from cellulosic feedstocks was supposed to be at 16 billion US gallons a year and corn ethanol 15 billion US gallons by 2015. At the end of 2010 over 90 percent of all gasoline sold in the U.S. was blended with ethanol. That number is probably higher now coming into 2021.
E10 is 10% ethanol and 90% gasoline. E15 has now become more popular as well and is between 11 and 15% ethanol. E15 is not recommended for motorcycles by the Renewable Fuels Association. Fun fact- Ducati will actually void your warranty for using fuel with ethanol content over 10% because it could severely damage the motor.
Okay cool. Now, why is ethanol bad for motorcycles specifically?
Ethanol LOVES water! Gasoline isn’t water soluble, but ethanol is. So not only can ethanol pick up water from the air, it can pick up contaminants as well. Once the alcohol in gasoline has picked up enough water (and contaminants) you’ll experience phase separation. Water and any accumulated sludge is heavier than the gasoline and sinks to the lowest point in the tank. Your fuel will have a shorter life span and obviously contaminants are not good for your engine. It can also rust your metal gas tank from the inside and can warp plastic ones. Rubber seals and fuel lines also do not fare well.
If your motorcycle is carbureted all that junk goes directly into them and can clog it up. Your motorcycle is now trying to run on water. Another effect of the oxygen from ethanol is that ethanol blends will run leaner than pure gasoline because there is more oxygen available in the fuel-air mixture. Ethanol is specifically terrible for carbureted motorcycles for these reasons.
There are not a whole lot of places where you can get ethanol free gasoline anymore. So what can you do to make sure your motorcycle runs properly when using the gas that’s available?
The answer is a combination of consistently riding your bike and using a fuel treatment to prevent phase separation. The “shelf life” of ethanol-gasoline blends is only 2 to 3 months. So if you ride your motorcycle regularly (at least running through a full tank of gas every month) and put fuel stabilizer in your tank when you are not riding as much, you should be in good shape. Do not blame ethanol for your poorly maintained motorcycle. There are tons of fuel treatments out there that will keep your gas stabilized.
If you have a carbureted motorcycle or dirt bike, you can also do some extra steps to ensure your carbs stay clean and clear after every ride. Once you are done riding the motorcycle, turn the petcock to the off position to stop the flow of gasoline to the carbs. Manually drain the carbs of that last bit of gasoline. If you can’t drain your specific bike you can run it until it runs out of fuel (just be aware that this can also potentially suck dirt into your carb if there is rust/debris already present in your gas tank).
I hope this article creates an understanding of how ethanol specifically affects motorcycles and what steps you can take to make sure your bike is running optimally.
https://www.pure-gas.org/ is the list of ethanol-free gas stations in the US