Overview of E10 Ethanol Gas Testing and Observations

This page provides a quick summary of ethanol gas testing and observations which I have performed over the past several years.  While I have additional data, the below links provide a look at a representative sample of observations that I have made.

My observations indicated that there is no information which suggests that use of E10 gas contributes to fuel tank swelling or other engine problems on the XR1200.  I have noticed sweilling of o-rings, seals, etc. when running non-ethanol race fuel - but the swelling goes back down when returning to use of ethanol pump gas.  Therefore, any fuel tank or system swelling may be attributable to other fuel additives in an area, but not to ethanol content of the E10 fuel.  Additional detail on these observations is provided in the below linked pages.

The following links provide details and observations on testing gasoline for ethanol content, possible separation of ethanol content from E10 gasoline over time, and the stability of the ethanol content of E10 gasoline.

For a discussion of E10 gasoline, and its stability over time, click here.
For a look at ethanol content testing of fresh E10 gasoline, click here.

For a comparative look at the results of ethanol content testing on non-ethanol fuel, click here.

For a look at ethanol content testing of stored E10 gasoline, click here.

E10 gas may have many drawbacks and contribute to lower engine performance and decreased gas mileage, but the observations which I have documented indicate that E10 gas will not generally separate simply due to prolonged storage.  E10 gas will separate if a substantial amount of liquid water is added to it (and therefore is not ideal for boating or aviation).  However, if one takes just the minimal amount of caution in filling a motorcycle fuel tank and keeps the filler cover in place so that liquid water is not added to the fuel, there is no reason that E10 gas should separate when used in the XR1200.
I have never had any problem with leaving unstabilized E10 gas in motorcycles stored for a year or more at a time.  (Or, in EFI cars stored for several years at a time.) And, the fuel injectors from motorcycles stored like this have not shown any significant blockage or gumming when sent to Marren for cleaning and blueprinting after extended use and storage.  While the octane value of the fuel appears to have fallen, and therefore it was important to drain and refill the fuel for engine protection, the fuel itself did not cause a problem during storage of the vehicles.
While storing motorcycles (and cars) with full tanks of E10 gas has not caused me any issues.  Non-ethanol race gas on the other hand, has caused rubber o-rings in the fuel systems of my motorcycles to swell.  Swelling from race gas has gone down after the race fuel is removed and these parts are allowed to dry out.
Also, the use of octane boosting additives for E10 gas has caused similar problems in Harleys (including the XR1200) in which I have used it.  Swelling has likewise gone down after the additives were removed and the parts have dried out.

So, while other fuel additives, including those regionally mixed into fuels by manufacturers, may cause fuel tank/component swelling, it is not indicated that the ethanol content of gasoline is the problem.

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