OME, 
  
You will mostly experience fuel consumption reduction when you use E10 as the ethanol fuel component has roughly half the calorific energy of 91. It's not unusual to see a 5% reduction in fuel economy. I won't comment about the savings using E10, other than to say there is no such thing! 
  
Personally I won't use E10 it in anything ... Politicians make poor petrochemists! 
  
Vev