Quote Originally Posted by green91
#2 make sure your ENTIRE fuel system is prepped for e85.. its highy corrosive and eats typical rubber lines etc. Need to make sure everything in your car is e85 safe including fuel pump, all lines and even your injectors/o-rings and everything in between.
For modern automobiles, I don't agree with this being as great a concern. There are a few guys who have been running it religiously without issue for quite some time now.

The bigger concern is having enough injector space. You will need to run 30% more fuel than you would.

On the flipside, you can run some fairly aggressive timing as e85 is pretty knock resistant.

A couple of issues to be wary of though. First, the injectors tend to "gum up" over time. The theory is that it has to do with the quality of the fuel itself. Some is just dirtier than others.
The other issue is oil contamination. Because you have to run 30% more than 91oct, it has been known to make your oil smell sweet. This is not good. To counter this, you will need to change your oil and filter a little more frequently.