Ethanol can be corrosive in a fuel system. It gets worst when it is allowed to interact with water, forming acids, and ethanol has a real affinity for water (hygroscopic), so you need to make sure the fuel system is well sealed. Further, without increasing static or dynamic compression (or both) ethanol burns colder, and liberates water without carrying as much out the exhaust stream when it burns, potentially contaminating the engine oil if the engine isn't driven long enough per cycle to heat the oil thoroughly and drive out moisture.
That isn't speculation, but comes from using 85% ethanol fuel for nearly three years (regularly since August, 2005). If you decide to do this, I'd strongly recommend using only PAO synthetic engine oil since it is more tolerant of acid formation and moisture, and provides better lubrication during those periods when there may be more moisture in the oil.
Also, plan on using either a lower alcohol percentage in cold weather, or using a supplementary gasoline enrichment system for cold starts if you live somewhere where the temperatures drop below 30ºF. I've had numerous cool mornings at anywhere from 25º to -10ºF when the engine would not start without excessive cranking and ridiculous enrichment until the compression heating got the cylinders warm enough to vaporize the ethanol and allow it to fire (just like cold cranking a diesel without glow plugs). Increasing the gasoline percentage to about 60% has proven sufficient to provide reasonable cold starts.
You may also need to either reprogram the PCM or change to injectors with a higher flow rating so the stock programming can satisfy the O² sensors within the maximum allowable (programmed) injector pulse width. I found that changing from 16.8 PPH to 19 PPH injectors was more than sufficient to end the constant P0171 (lean exhaust) error codes I would generate at almost every run cycle. Similar results can be achieved through increasing fuel pressure by altering the fuel pressure regulator. So long as the O² sensors do not achieve too high a signal and produce sufficient crosscounts while the PCM does not have to pulse them longer than the allowable maximum, the PCM should not set any error lean codes.
If you drive a lot of short trips, it might not work out well for you in cooler weather. I drive about 40 highway miles daily, and over three years have averaged 22.4 MPG on "regular" gasoline (10% ethanol) compared to 19.3 MPG on 85% ethanol. Even though the mileage is lower, the cost differential of $1.00/gallon makes driving on E-85 a lot less expensive in cost/mile. My current running average is 17.2¢/mile on gasoline, 14.8¢/mile in E-85.
From last week:
