Octane or Ethenol
Road Warrior
Joined: Nov 2010
Posts: 1,870
Likes: 4
From: Jacksonville, FL
As long as automotive fuel is stored properly in an enclosed container like an airtight fuel tank, it will maintain its usability indefinitely regardless of the ethanol content. Evaporation and exposure to air is what causes fuel to degrade. Not how long it is stored. Unlike carbureted engines, most EFI systems are sealed from exposure to air.
So in a bikes fuel tank, condensation occurs. To what extent it occurs will be based on temp and humidity fluctuations. But over time (sitting unused) some amount of water will build up in that tank. And no amount of riding and shaking will mix Gas and Water. Due to the weight and density of water, it's going to settle to the bottom of the tank..... which is where most pick up tubes and pumps are and presto, now you have a problem. Might be a small or large problem, but it is a problem.
Outstanding HDF Member
Joined: Dec 2008
Posts: 2,007
Likes: 353
From: Ohio
Although I understand what you're saying, it's my understanding that part of the problem with Ethanol fuel is water separation.
So in a bikes fuel tank, condensation occurs. To what extent it occurs will be based on temp and humidity fluctuations. But over time (sitting unused) some amount of water will build up in that tank. And no amount of riding and shaking will mix Gas and Water. Due to the weight and density of water, it's going to settle to the bottom of the tank..... which is where most pick up tubes and pumps are and presto, now you have a problem. Might be a small or large problem, but it is a problem.
So in a bikes fuel tank, condensation occurs. To what extent it occurs will be based on temp and humidity fluctuations. But over time (sitting unused) some amount of water will build up in that tank. And no amount of riding and shaking will mix Gas and Water. Due to the weight and density of water, it's going to settle to the bottom of the tank..... which is where most pick up tubes and pumps are and presto, now you have a problem. Might be a small or large problem, but it is a problem.
I guess I got lucky and have had "special" production bikes. I had an 01 RK and used the cheapest gas I could find and never had any issues. It even set for a year a couple times while i was "over there", came home, hooked the battery up and fired right up. I still run the cheapest I can find in my 09 EFI... No issues yet.. Maybe we just have better gas down here...
"ETHANOL fuel is a mixture of ethanol (Grain alcohol) and unleaded gasoline. While ethanol does have an impact on fuel mileage, fuels with an ethanol content of up to 10% may be used in your motorcycle without affecting vehicle performance."
Even though the above is in the manual, it simply is not true.
91 octane withOUT ethanol will run stronger (most will feel it in seat of the pants, and a dyno will also show it) than 91 octane with ethanol.
Also, you will note in the quote that it says "may be used", but it is not required.
I have found that 89 octane without ethanol will run stronger (with no pinging/pre-detonation/no timing retardation) and get better mpg than 91 with ethanol.
I have found that 87 octane with no ethanol does cause pinging/pre-det/timing retardation in high load and/or high heat.
I run 91, 92, or 93 octane with or without ethanol, and sometimes 89 without ethanol...depending on what is available.
If I have to fill up with 87 because that is all that is available I use an octane booster.
Even though the above is in the manual, it simply is not true.
91 octane withOUT ethanol will run stronger (most will feel it in seat of the pants, and a dyno will also show it) than 91 octane with ethanol.
Also, you will note in the quote that it says "may be used", but it is not required.
I have found that 89 octane without ethanol will run stronger (with no pinging/pre-detonation/no timing retardation) and get better mpg than 91 with ethanol.
I have found that 87 octane with no ethanol does cause pinging/pre-det/timing retardation in high load and/or high heat.
I run 91, 92, or 93 octane with or without ethanol, and sometimes 89 without ethanol...depending on what is available.
If I have to fill up with 87 because that is all that is available I use an octane booster.
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Road Master
Joined: May 2012
Posts: 1,140
Likes: 6
From: Arkansas
I think that we are all "already" in agreement with that. The problem is, it's getting more and more difficult to find "ethanol free" gasoline. And I've been seeing more and more stations with ethanol ratings of 15% and more. My local station that advertises "ethanol free gasoline" just recently stoped carrying premium gas. So now I'm stuck running 10%. And, for me, the verdict is still out on boosters. As for winter storage ( if necessary ). I just simply use "Stabil".
Stellar HDF Member
Joined: Aug 2012
Posts: 2,134
Likes: 1,871
From: Minnesota
Ethanol actually acts as an absorber of water because it mixes with it in any proportion and does not separate. Prior to ethanol in gas, motorists added an alcohol based liquids to their tank to absorb water and prevent the gas lines from freezing in the winter. Frozen gas lines are rare now due to the use of ethanol in fuels.
Heet (isopropel alcohol) was very popular in Minnesota winters, because the alcohol/water mix would not freeze in the gas line, not because it mixed the water and gas.
Regarding "an airtight fuel tank" I am not convinced they are air tight, if they were, they would build up pressure in the heat and vacuum when it cools off. Thus I would expect that some air enters and exists the tank as temperature changes. Thus it is best to store a bike with a full tank - less air- less condensation - less water entering the system.
Road Warrior
Joined: Aug 2009
Posts: 1,432
Likes: 0
From: Central Florida, USA
As long as automotive fuel is stored properly in an enclosed container like an airtight fuel tank, it will maintain its usability indefinitely regardless of the ethanol content. Evaporation and exposure to air is what causes fuel to degrade. Not how long it is stored. Unlike carbureted engines, most EFI systems are sealed from exposure to air.
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Joined: May 2013
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