Is Ethanol bad for motorcycles? An Engineer’s Explanation

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I’m an engineer for an oil and gas company and some of the false truths circulating around the internet about ethanol need to be put in check.  I’m also a gear head at heart and spend every day after work in my garage, so I’m going to give an unbiased and straightforward answer about what ethanol is and isn’t.

Is ethanol harmful to motorcycles? E10, which is gasoline containing up to 10% of ethanol, is not a good fuel choice for small engines or motorcycles.  Ethanol fuel is less stable than gasoline, has a shorter shelf-life, causes more carbon buildup, gums up carburetors and eats away rubber parts quicker than ethanol-free fuel.

In fact, I wouldn’t recommend ethanol fuel for any carbureted vehicle.  But fuel injected vehicles are a different story, I’ll explain more about fuel injection later.

What is Ethanol??

Ethanol or ethyl Alcohol is a refined chemical found in alcohol and over-the-counter disinfectants.  Its chemical formula is C2H6O, and easily mixes with unleaded gasoline.

Fuel must meet certain chemical specifications before it can be sold at gas stations. It cannot have more than a certain sulfur content. It must also have a precise freezing point and a tight tolerance for its octane numbers.  To ensure that the fuel meets all specifications, samples are pulled from every line.

Raising a product’s octane number is expensive.  It is more costly to produce a product with a higher octane number.  The octane number of ethanol ranges anywhere from 100-135, that’s why adding a little bit of ethanol to gasoline can boost its octane number from 80 to 85 or 87, which is what customers see at the pump.

Ethanol is a gasoline additive that boosts octane. There are pros and cons to its use in small engines which I’ll discuss further.

Ethanol: Misconceptions

There is a lot to learn about ethanol online.  No, it’s not going to ruin your engine if you use it, oil refineries wouldn’t be using it as an octane booster if that were the case. This would cause them to lose their reputation and stock prices will plummet.

Ethanol is not a way to raise gas prices. In fact, it can do the opposite. Ethanol is a cost-effective way of boosting your fuel’s octane number.  Other ways to increase octane are more expensive and would lead to higher gas prices at your pump.

Refineries can produce ethanol for a very low cost.  By using ethanol to increase the octane, oil refineries can keep gas prices low for customers. This ensures that the fuel meets all government specifications before it leaves the station.

It’s not a new concept to add Ethanol to gasoline. It has been a pretty common thing since the 1920’s in order to boost the octane of fuel used in wars, racing applications, and many other purposes. Gas companies have done a good job at being more transparent about its use, that’s why it has become more of a point of contention in the last 10 years.  If not for the 10% ethanol sticker at the pump most people wouldn’t think twice about it.

Many believe that ethanol burns cleaner than conventional gasoline and is more harmful to the environment. The opposite is true. Ethanol can be fully biodegradable and emits less greenhouse gases than other fuel additives.

This PDF, published by the US Department of Energy, contains more myths about gasoline ethanol.

Ethanol is bad for carbureted motorcycles?

I would not recommend using alcohol in any vehicle with a carburetor.  My college tuition was paid for by me rebuilding motorcycles and doing repairs for others.

Nearly 100 carburetors have been rebuilt, most of them for motorcycles. I believe that ethanol-free fuel would have saved people the majority of their problems. Also, they should have emptied the carburetor before they park their bike for the winter.

Ethanol absorbs water easily, unlike other gasoline. It also has an even shorter shelf life that ethanol-free gasoline, making it a dangerous combination for carburetors. Even if the ethanol fuel is kept in the carburetor for a few weeks, it can form a gel-like substance that can clog all carburetor jets. This will require a complete rebuild.

I get a lot of questions from coworkers and friends about their motorcycles and classic vehicles when they won’t start.  My first questions are: “Is the battery fully charged to 12.6 volts?”, “Is it carbureted?”?, and “Do you use ethanol-free gas?”

And almost always they tell me that they can’t remember what type of fuel they put in last time it ran.  If they had put in ethanol-free fuel religiously, they’d be able to recall.

This is true for lawn mowers and weed eaters as well as chainsaws and other small gas-powered machines.  Those small carburetor jets get plugged so easily and if you use ethanol fuel, you’re just asking for those jets to gum up.

A video series has been created about how to restore motorcycles. It includes a 25-minute video detailing how to clean and rebuild carburetors using ethanol gas. The series also covers other difficult-to-tackle parts such as electrical and body work. I give dozens of tips and tricks that you won’t find anywhere else online. Click here for more information if you’re interested in viewing multiple videos that will help fix up your bike or if you’re interested in completely building your dream motorcycle!

Is Ethanol Bad For Fuel InjectWhat are ed Motorcycles?

Different answers are available for fuel-injected vehicles.  Ethanol isn’t nearly as harmful for fuel-injected cars. In fact, I use 85 octaneethanol fuel almost exclusively in my daily driven Jeep. High pressure fuel injection pushes out any clogs in the injectors.

In that they deliver the correct amount of fuel to the motorcycle’s engine, fuel injectors can be compared to carburetors. However, unlike a carburetor a fuel injector can be electrically powered. The ECU is equipped with several sensors that monitor the motorcycle’s fuel consumption. The ECU also needs to inject fuel, which is the main difference from a carburetor.

You can do the same thing as I do with my Jeep if you have a motorcycle that is fuel-injected.  Every 5Th Or 6Th I fill up my Jeep with 91 octane, ethanol-free fuel at one of the top tier stations like Shell, Chevron or Exxon every time I go to the station. All stations at the top of the line have their own additives that clean your intake manifold, valves and cylinders.

You don’t have to use those high octane fuels exclusively in order to enjoy their benefits. A fuel-injected motorcycle will only need to have a few fill-ups of high octane gasoline. Unless you have a high-compression or high performance engine that strictly calls for 91+ octane ethanol-free fuel, then be sure to follow your manufacturer’s directions.

Ethanol and engines:?

To achieve the best fuel economy, all EPA government tests for new cars and motorcycles are done using high octane ethanol free fuel. Ethanol fuel has a lower gas mileage than ethanol-free fuel. Ethanol fuel will give you a fuel consumption that is between 2% and 5% lower.

Ethanol tends leave more carbon buildup in pistons and valves that ethanol-free fuel. This is why I recommend ethanol-free fuel at a minimum of every 5Th-6Th fill up for fuel injected motorcycles (and for every fill up on carbureted motorcycles), so it can clean all those high heat parts effectively and the carbon doesn’t continue to build up.

Realistically, the amount of time you spend riding your motorcycle is more damaging than using ethanol fuel.

What type of fuel should you use for your motorcycle?

My motorcycles are all older carbureted bikes so I do not use any ethanol.  People choose to fill their motorcycles with 91+ octane fuel, which is ethanol-free, every time they need it. That’s an excellent way of taking care of the fuel delivery system.

Filling up a motorcycle is only a few gallons, so the price doesn’t really make that much of a difference. It is worth getting the best fuel. The increased fuel economy and mileage that motorcycles achieve almost make up the difference for the extra cost of ethanol-free fuel.

Because of the potential for serious injuries if something goes wrong, I prefer to be safe when riding my motorcycle.  For example, a misfire.  Ethanol fuel is less likely to cause an accident and can lead to driver jerking and losing control.

You can be sure to use high-octane, ethanol-free gasoline every time you fill up. See my other article to learn more about the right fuel for your motorcycle.

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