Ethanol
Questions and Answers
1 What is ethanol?
2 When is ethanol added to gasoline?
3 What is E10 fuel?
4
What are the negative properties of ethanol?
5 What issues are caused by ethanol’s attraction to
water?
6 What happens when phase separation occurs?
7
Can I use the gasoline remaining after removal of the phase separated
water and alcohol?
8 Can phase separation be reversed?
9
Wouldn’t the cleaning properties of ethanol be good for a fuel system?
10
Are Yamaha engines compatible with E10 fuel?
11
Can I use fuel with a higher percentage of ethanol, such as E15 or E85?
12
Why do boats seem to have more issues attributed to E10 fuel than cars?
13 How long can E10 fuel be stored?
14 What can I do to prevent issues with E10 fuel?
In addition, this information
was taken from the Yamaha Outboard FAQ section of their website.
You may
visit this section
of their website by clicking here
for additional topics of interest. Also, some answers have been
updated with information
provided by the Yamaha Marine Group "The Boater's Log", Volume 1, No. 1.
Question 1
What is ethanol?
Answer
Ethanol is highly refined alcohol that is made from grain
(typically corn) or the cellulose from other plants.
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Question 2
When is ethanol added to gasoline?
Answer
Ethanol is added to gasoline by local or regional
distributors.
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Question 3
What is E10 fuel?
Answer
E10 fuel is a blend of ethanol (10%) and gasoline (90%).
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Question 4
What are the negative properties of ethanol?
Answer
Ethanol has several properties that contribute to
fuel system issues.
- Ethanol is a strong cleaner (solvent).
- Ethanol is hygroscopic (e.g., it has a strong attraction to
moisture).
- Ethanol produces less energy (BTU's) than an equivalent unit of
gasoline.
- E10 fuel’s usable life span may be less than the normal length of
off season boat storage.
- Ethanol will clean gum and varnish as well as surface corrosion
from any surface it contacts in the boat fuel system as well as storage
and transport tanks in the fuel distribution system.
- Ethanol will increase the amount of water accumulating in fuel
tanks.
- Ethanol my dissolve plastic resins used to make some fiberglass
fuel tanks.
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Question 5
What issues are caused by ethanol’s attraction to water?
Answer
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 breakdown and the ethanol molecules will attach
to the water molecules. This is called phase separation.
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Question 6
What happens when phase separation occurs?
Answer
Several things happen:
- 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.
- Fuel for the engine is drawn from the bottom of the tank. An
engine will not run properly, if at all, on ethanol and water. The
ethanol and water mixture is very corrosive to some metals and can
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 the requirements of the
engine.
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Question 7
Can I use the gasoline remaining after removal of the phase
separated water and alcohol?
Answer
No, the remaining gasoline will have a lower octane level that
may not be compatible with your engine.
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Question 8
Can phase separation be reversed?
Answer
No, there are no additives or processes that will recombine
phase separated ethanol and gasoline.
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Question 9
Wouldn’t the cleaning properties of ethanol be good for a fuel
system?
Answer
No, fuel systems that have been used for non-oxygenated gasoline
will have varnish depos¬its and surface corrosion (rust and
aluminum oxides). This includes the tanks and pipes used for fuel
storage and transportation. Ethanol will clean varnish as well as
surface corrosion from any surface it contacts. Ethanol may dissolve
plastic resins used to make some fiberglass tanks. The amount of
material cleaned from all of these systems can quickly exceed the
filtration capacity of fuel system filters resulting in restricted fuel
flow. Ultimately engine performance is reduced and potentially damage
to the engine can occur.
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Question 10
Are Yamaha engines compatible with E10 fuel?
Answer
All current models as well as most engines built since the late
1980’s have been designed with fuel system components that are tolerant
to fresh fuel containing ethanol up to 10% (E10). Outboard fuel systems
can still be affected by: water, dissolved gum, varnish, corrosion
particles, and dissolved resins that E10 fuel has cleaned from the
distribution system and your boat’s fuel tanks.
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Question 11
Can I use fuel with a higher percentage of ethanol, such as E15
or E85?
Answer
No, all of the negative issues discussed in this FAQ section
will be increased and may cause major damage to the engine.
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Question 12
Why do boats seem to have more issues attributed to E10 fuel than
cars?
Answer
Cars are having issues but are somewhat more
tolerant due to typical usage patterns and differences in their fuel
systems. Major differences are:
- Modern automotive fuel systems (fuel filler, fuel tank,
distribution lines and engine components) are closed or non-vented.
Once the fuel is pumped into the tank, there is very little circulation
of outside air (containing moisture) into the fuel system.
- Boats are operated and often stored in a very wet environment
increasing the risk of water directly entering the fuel system.
- Boats have vented fuel systems which allow moisture laden air to
circulate into the fuel tank as the fuel is drawn out of the tank and
as the fuel expands and contracts during heating and cooling cycles of
the outside air.
- Automotive fuel tanks are typically much smaller than boat fuel
tanks and are refilled more frequently. A full tank of fuel in a car or
truck, typically 20 ~ 40 gals, may be used and refilled every week or
two. Boat fuel tanks, typically 40 ~ 100+ gals per tank, may only be
refilled once a month during the boating season and typically may sit
unused for many months during the off season.
- Some boats use fiberglass fuel tanks. Polyester resins can be
dissolved by ethanol.
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Question 13
How long can E10 fuel be stored?
Answer
There are many different opinions concerning how long it is ok
to store any fuel (E10 fuel or gasoline), 2 weeks, 90 days, 1 year, or
longer, before losing the properties that are required for proper and
safe operation of your engine. There are too many variables (e.g., the
age of fuel when purchased, temperature, humidity, use of stabilizers
and the type of storage containers) to accurately predict how long.
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Question 14
What can I do to prevent issues with E10 fuel?
Answer
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:
- If at all possible, do not use E10 fuel.
- Ideally (before switching to E10 fuel) have your fuel tank
completely drained to remove any accumulated water. As little as 16 oz.
of water can promote phase separation in 25 gals of E10 fuel. The
result would be 2.75 gals of unusable ethanol and water mixture on the
bottom of the tank.
- If the tank can be completely drained, the internal surfaces
should be mechanically cleaned to remove rust or aluminum oxides. Fuel
polishing companies may be able to provide this specialized service.
- Consider replacing the fuel tank in an older boat.
- If your boat has fiberglass fuel tanks built prior to the early
1990’s, consult with your boat builder concerning E10 compatibility.
- If unable to completely drain and clean your tank before
switching to E10 fuel, add as much E10 fuel as possible to minimize the
possibility of phase separation. Example: 16 oz of water may cause
phase separation in 25 gals of E10 but 16 oz of water in 30 gals would
be safe from phase separation.
- Install a Yamaha
10-micron water separating/fuel filter between the boat’s fuel tank
and the engine.
- Change the 10-micron filter every 25 hours of use until there are
no indications of excessive water and contaminates collecting in the
filter. Normal filter changes are recommended every 50 hours of use.
- Carry extra filters and change more frequently if there are
indications the efficiency of the filter is rapidly diminishing due to
excessive water and contaminates.
- 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.
- Occasionally, test your fuel to verify the amount of ethanol is
not higher than 10%. The blending of ethanol with gasoline by
distributors is not a precision process. Inexpensive test kits are
available, GOOGLE E10 Fuel Test Kit.
- Regularly use Yamaha
Fuel Stabilizer to retard fuel aging.
- Stabilize fresh fuel before storing. Stabilizers do not help fuel
that has already aged. Stabilizers are most effective when immediately
added to fuel fresh from the gas station or marina fuel pump.
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