There is often no savings by using E85. The fuel efficiency of E85 is much lower than regular fuel.

“28% fewer MPG than gasoline”
SOURCE: http://en.wikipedia.org/wiki/E85

If the price is 28% lower ,that is break even price in cost per mile. Since efficiency is lower one will also need to refuel more often.

If 87 regular is $3.59
The break even price for E85 is $2.58.
Any price above $2.58 is costing the user more money per mile that 87 Regular [total $ spent on fuel for the year will be higher too].

The 28% fewer mpg is based on BTU formula alone and nothing else. There are many factors that affect MPG other than BTU. E85 contributes to more complete combustion and because of the 105 octane, your engine timing will not retard due to any knocking that may occur from using lower octane fuel. There was also a ground breaking study that showed that using certain blends of ethanol maintained or even increased MPG. http://www.ethanol.org/news/index.php?newsid=25 Also, it’s been documented that the average mpg loss varies 5-15% on OEM Flex Fuel Vehicles. The cost of E85 needs to be 15% cheaper to break even for those who may lose that much and in some states it’s currently 30% cheaper http://www.e85prices.com. Those estimated losses are based on E85 tuning by the OEM which is not very good. The AfterMarket kits may give you much better MPG performance because it is tuned for E85. As stated before, there are many factors that contribute to MPG, so unless you can test the exact same route, using the exact same driving conditions (accel, decel, temperate, tire inflation, wind, etc), your comparison may be apples to oranges. My customers are not complaining about MPG and love the improved performance. I have 2 customers with Avg Fuel Economy readout’s on their message centers, that disputes the MPG loss. They have actually gained in MPG. I cannot guarentee the MPG you will get, but for those that have choosen to see for themselves, they are happy with thier decision to convert.

Thanks for the comment and information, David. It is definitely worth weighing all of your options before purchasing a conversion kit, or a car with FlexFuel ability, and looking into break even points and the average prices of E85 and regular gasoline. I filled up with regular yesterday for $3.57/gallon and today saw most gas stations offering regular fuel for $3.75/gallon (glad I got it yesterday!), while E85 prices seem to be hovering at the same prices as yesterday, so I guess it just depends. I was not aware that the fuel efficiency is lower on E85, so thank you for passing that info. along.

Since E85 is only 15% gasoline, it does offer significant advantages over regular gasoline in terms of being more eco-friendly, though.