In general, I think it's a good idea; anything to get away from dependence on foreign oil (or just petroleum products, for that matter), but as of right now, there are not that many E85 dealers around the U.S. IMHO, any conversion kit you would buy today would have to be capable of switching from E85 to regular gasoline and back easily. Like a switch on the dash. Ideally, it would be able to use a mix of E85 and gasoline, as we seldom ever drain our tanks completely and they may have 1/4 or even 1/2 a tankful left in them when we fill 'er up. Also, considering that E85 has only about 70% the energy content of gasoline, you will use significantly more of it to get from point A to point B. How long is the payback period? There are too many variables to come up with a reasonable number of months/years or miles driven.
Perhaps I'm misinformed or missing something, but I fail to see how there is any savings to E85.? I've seen one place that sells it.? It is the same price as gasoline, more if you shop around for gasoline.? As mentioned above it is about 70% the efficiency of gasoline, so fuel economy suffers.? I sell cars.? We have a 2007 in the line that is E85 compatible.? It is rated at 21-25 mpg with E85 vs. 23-30 mpg for the all gasoline version. That's better than the 70% figure above, but obviously there is no savings in that instance.
The new clean diesel offers significant savings, but you can't convert a gasoline engine to it.
This topic has come up in depth at a couple other car forums I frequent, and the short answer is this: there is no short-term cost benefit right now. Even in my area where E-85 is somewhat available and a little cheaper than regular gas, the lower economy / power nullifies all savings. Additionally, there can never be a complete switch-over to E-85 because there's not enough corn grown in the United States to produce as much fuel as we use. Some of that corn has to be saved for eating anyway. Similar cost-benefit results for hybrid vehicles... the gas savings do not make up for the higher cost of the vehicle/parts/maintenance. It's the long-term perspective that you have to consider, as Karl stated. More alternative fuel options = higher use of those alternatives = less dependence on foreign oil = everything will be cheaper (since oil will be in lower demand, and alternatives will be more widely available). We're in the infant stages of this movement, and it will likely be several years before it starts to work itself out.