At current $2.43 for regular in my area, my 2015 2500 6.0 averages about 14 mpg for all miles for a cost per mile of just over 17 cents a mile. The same vehicle gets about 11 mpg average with E85. So the break even price for E85 is about $1.87. It is currently at $1.70 in my area, so it is a net gain per mile to use it. Several years ago when we had $4 regular gas, E85 was a steal. I could get it $1 to $1.50 a gallon cheaper. My vehicles lived on E85 for a couple of years. It is why I prefer flex fuel vehicles. I like options as prices fluctuate.