Martin, have you read this entire thread?
I thought I had already explained "why E10" a long time ago.

The only reason E10 is on the market is, blending stations ( oil companies ) get* the maximum tax credit for 10% ethanol.

They could use more, but there is no $ advantage to it.
EPA has tested and approved E20 and E30 as meeting all air quality requirements, when used in any engine. Lawnmower on up. ( so EPA is ok with it, but auto makes have not taken the step to approve or not approve )

Stations in CA use 5.75% ethanol, but get only 57.5% of the tax credit.

5.75% ethanol is a 1:1 replacement for MTBE.
So really, in the past, to meet EPA standards for oxygenates, blenders needed to only add 5.75%. For some odd reason, lawmakers in Washington made the credit good on a pro-rata basis up to 10% ethanol.
( years ago )

Thus, big oil companies went to big auto companies and said "would you please certify all your cars for 10% ethanol?" And they did.

The quote in the previous post is false. ( I thought I mentioned that earlier also... ) Ethanol is not bad for pipes!!! Ethanol is less corrosive than water! Old, dirty pipes that have ground water already in them are bad for ethanol! Ethanol will actually clean the pipes, and remove the water in the pipes, but then you end up with wet, dirty ethanol that you should not put in any car!

I got one of the earlier ( cheaper ) models from here earlier this week.
http://www.change2e85.com/servlet/StoreFront

Funny... I posted eariler that in Minnesota the pumps say "Minimum 85% ethanol" but after my water test, they really sell E70.

I just got some "E85" in Colorado.
The Colorado pumps say "Minimum 70% ethanol".
When I did the water test, Colorado is selling 82.5% ethanol at the pump.... in winter....

Go figure.

I had ~4 gallons of plain gas left, and I just filled up with 11 gallons of E82.5.

So that makes it.... about E60. I have about 60% ethanol in my tank now.

I ran up to 40% without issues before I had "the little box".
Ran fine on the trip home, but that was only 4 or 5 miles on an already hot engine. -John

*or used to get. I'm unclear about the current tax incentives