E10 fuel, a mixture of 90% gasoline and 10% ethanol, has been introduced into various regions of the United States and, in many locations, E10 fuel is the only type available. The Environmental Protection Agency (EPA) has implemented Ground Level Ozone Air Quality standards. Part of the EPA’s strategy to meet these standards requires the addition of fuel oxygenates to gasoline to improve the internal combustion process. Ethanol or MTBE (Methyl Tertiary Butyl Ether) are approved fuel oxygen­ates. Ethanol has a very high octane rating and, when mixed with low octane unleaded gasoline, increases the octane level of unleaded gasoline.

Ethanol also has some less desirable properties that are explained below. MTBE does not have negative effects on engine fuel systems but does have some negative environmental issues; it does not biodegrade easily and is a suspected carcinogen. MTBE contamination from leaking under­ground fuel storage tanks has been detected in ground water supplies. Many states are now prohibiting the use of MTBE.

The following questions and answers will provide important information regarding the use of fuel containing ethanol.

Q. Are Yamaha engines compatible with E10 fuel?
A. Yes, all current models as well as most engines built since the late 1980s have been designed with fuel system components that are tolerant to fresh fuel containing ethanol up to 10% (E10).

Q. Can I use fuel with a higher percentage of ethanol, such as E15 or E85?
A. No, all of the negative issues discussed below will be increased and may cause major damage to the engine.

Q. What are the properties of ethanol in E10 fuel that make it less compatible with fuel systems than straight gasoline?
A. Ethanol has several properties that contribute to fuel system issues: • Ethanol is hygroscopic - it has a strong attraction to water and absorbs the moisture from the air • Ethanol is a strong cleaner (solvent). • Ethanol produces less energy (BTUs) than an equivalent unit of gasoline.

Q. What issues are caused by ethanol’s attraction to water?
A. Ethanol molecules have a stronger bond to water molecules than to gasoline molecules. In the absence of water, ethanol and gasoline molecules will bond. When water is added to E10 fuel, the bond between the ethanol and gasoline will weaken. When the percentage of water in E10 fuel reaches approximately 0.5%, the bond between the ethanol and gasoline molecules will break and the ethanol molecules will attach to the water molecules. This is called phase separation. The ethanol and water molecules settle to the bottom of the fuel tank forming a distinct layer of water & ethanol on the bottom and gasoline without ethanol on the top. As little as 1.6 oz. of water can promote phase separation in 2.5 gals of E10 fuel. The result would be 33.6 oz. of unusable ethanol and water mixture on the bottom of the tank.

Q. What happens when phase separation occurs?
A. Several things happen:
• Fuel for the engine is drawn from the bottom of the tank. An engine will not run properly, if at all, on the ethanol and water mixtures.
• The ethanol and water mixture is very corrosive to some metals and can cause corrosion or rust in the fuel tank and damage internal engine components.
• The remaining gasoline, without ethanol, will have an octane level below the original E10 fuel’s octane level, approximately 2~3 points lower. This octane level may be below engine requirements.

Q. Can phase separation be reversed?
A. No, there are no additives or processes that will recombine phase separated ethanol and gasoline.

Q. Can I use the gasoline remaining after removal of the phase separated water and alcohol?
A. No. The remaining gasoline, without ethanol, will have an octane level below the original E10 fuel’s octane level, approximately 2 ~ 3 points lower. This octane level may be below the requirements of the engine.

Q. What issues are caused by ethanol’s strong cleaning (solvent) properties?
A. It is normal for gasoline to leave varnish deposits and for surface corrosion to occur inside the tanks and pipes used for fuel transportation and storage: rust on steel and oxides on aluminum. Ethanol will clean any varnish as well as rust and oxides from any surface it contacts. Gasoline without ethanol does not clean the varnish, rust or oxides. Since ethanol is added at the distributor facilities, it will clean any storage pipes and tanks, truck tanks, gas station storage tanks and your engine fuel systems. The amount of material cleaned from all of these systems can quickly exceed the filtration capacity of filters located in fuel systems resulting in restricted fuel flow. If these clogged filters are not replaced, engine performance is reduced and potential damage to the engine can occur.

Q. What issues are caused by ethanol’s lower energy content (BTUs) than an equivalent unit of gasoline?
A. E10 fuel will produce approximately 3% less power than gasoline. This is not enough to be noticed in most applications. Q. How long can E10 fuel be stored? A. There are many different opinions concerning how long it is okay to store any fuel (E10 fuel or gasoline), 2 weeks, 90 days, ???, before losing the properties that are required for proper and safe operation of your engine. There are too many variables, such as the age of fuel when purchased, temperature, humidity, use of stabilizers and the type of storage containers to accurately predict how long.

Q. What can I do to reduce or prevent issues with E10 fuel?
A. Total prevention of issues may not be possible but there are steps you can take to minimize the occurrence and severity of the negative affects of E10 fuel:
• Remove any accumulated water from the fuel tank periodically (water in fuel can cause microorgan- ism growth.
• Avoid mixing E10 and MTBE gasoline blends. Mixing may cause precipitates to form which can clog filters.
• Do not drain a used filter and reinstall. Contaminated fuel can enter the filtered side of the filter while draining.
• Buy name brand fuel.
• Buy fuel from the same source if possible.
• Buy fuel from stations that have newer, cleaner storage tanks.
• Avoid storing fuel in a vented container such as a motorcycle fuel tank or vented gas can (reduces evaporation of vital fuel components).
• Keep stored fuel in as cool an area as possible (reduces evaporation of vital fuel components).
• Regularly use Yamalube Fuel Stabilizer and Conditioner to retard fuel aging.NOTE: Stabilizers do not help fuel that has already aged. Stabilizers are the most effective when immediately added to fuel fresh from the gas station. Without the use of a fuel stabilizer, fuel can deteriorate in as little as 2 weeks and begin to clog jets. Clogged jets due to bad fuel are not covered under warranty.
• Ensure stabilized fuel is circulated through all of the engine’s fuel system components prior to storage. • Drain fuel from carburetors that have open air vents.
• Store fuel tanks approximately 7/8 full, minimizing the amount of air space above the fuel inside the fuel tank. Storing completely full may allow some fuel spillage as the fuel expands during hot weather. Do not attempt to seal a vented fuel system. The inability to vent could cause damage to the fuel tank or other fuel system components.
• Minimize the time fuel is allowed to age in your fuel tank or other storage containers.
• Do not attempt to use fuel with ethanol content higher than 10%. If in doubt of the ethanol content of the fuel, test the fuel to verify the amount of ethanol is not higher than 10%.

Inexpensive test kits are available. A web search will provide many sources. Just type: E10 Fuel Test Kit.  

Ride Safe and Smart!
Dr Jay