Gas Mileage vs Engine Mode

[nsmiller]

As far as I understand it, the only real factor that matters with fuels is the octane rating, sometimes called RON. Petrol companies blend fuels depending on spot market purchases, so the actual composition varies, but they have to hit the RON value consistently.  
Adding ethanol is purely to meet bio fuel regulations, to lower overall global warming potential of the fuel. To compensate for adding ethanol, other alkanes are added to maintain the RON rating. It should not therefore have any impact on your fuel range.

Ethanol is not as energy dense as gasoline, so it will decrease your engines power and fuel economy, but whether or not the difference in fuel economy justifies the additional price is debatable.

[keithu]

The environmental benefits of ethanol are also debatable, but that's another topic. The reality is that in many parts of the USA - especially the west - it's hard to find any fuel that isn't E10.
 
Fortunately modern vehicles like our FJ-09 are designed to run on E10, so we shouldn't experience things like fuel line deterioration, tank deformation, and other problems that were common as little as 10-15 years ago.
 
I go out of my way to get ethanol-free fuel for my carbureted lawn mower, but for the FJ I think it is a waste of money.

[berryber]

Ethanol does have less energy then gasoline. So adding it to our fuel does lower our MPG. The 10% most of us get is only supposed to get 3% less mileage. I think its a little worse then that ,but have no real proof.

[BBB]

Yep, 3% drop in mileage is the official figure. So, 1.2 miles less per gallon if you do 40 mpg. Probably way less than the variation you get from riding styles.

[estell]

I have noticed a difference in fuel mileage with the temperature. If the temps are in the 40s then the coolant temp doesn't get much above 155F. I expect that the ECU commands a rich fuel mixture at temperatures that low. That results in lower fuel mileage than I see when the coolant temp gets up to 180 or more.

[nsmiller]

I have noticed a difference in fuel mileage with the temperature. If the temps are in the 40s then the coolant temp doesn't get much above 155F. I expect that the ECU commands a rich fuel mixture at temperatures that low. That results in lower fuel mileage than I see when the coolant temp gets up to 180 or more.

I totally agree. Temperature makes a big difference. Also differences in summer and winter fuels.

[alejandro]

Maybe ten years ago? or whenever it was that E10 first showed up in the US, I believe that it melted the plastic gas tanks on some Ducati Multistradas, causing a whole lot of grief. Does anyone remember the details?

[blindjoebeck]

Maybe ten years ago? or whenever it was that E10 first showed up in the US, I believe that it melted the plastic gas tanks on some Ducati Multistradas, causing a whole lot of grief. Does anyone remember the details?

The tanks on the first generation Multistradas (air-cooled, two valve motors) would expand over time. The tanks were long and extended back under the seats so if they expanded they no longer fit in the frame and the attachment points didn't line up.  In the USA, there were enough affected bikes and lawsuits and such that there was a class action suit and Ducati announced that they would provide one free replacement tank on affected bikes. I had a 2008 1150S but didn't have any problem with the tank. 
-- Joe
 

[chamelion]

Here in Australia I use 98ron (no ethanol) exclusively. I have found no appreciable difference in economy regardless of mode.