The E15 will do NOTHING for fuel mileage, it may/will be cheaper per gallon. Typically using 10% you'll lose 10% mpg so I'd assume 15% you'll lose 15%. The only one that gains from the use of ethanol as fuel is the farmer growing the corn.
Danny & Linda
Sold our '13 Thor Redwood 36 FB
Currently RV & truckless
Read everything and then think about what brand of gas you want to buy, there is a difference!
Straight gasoline has 114,500 btu's per gallon, ethanol E85 has 81,800 btu's per gallon. Bottom line is the more ethanol you add to gasoline the less thermal energy is produced whic means less power and miles per gallon of fuel.
__________________ USMC Veteran
FMCA 101070S Dave & Myra One day your life will flash before your eyes,
make sure it's worth watching!