For grins I set my cruise at 55mph today for a 8 mile stretch of mostly flat (small rolling hills) highway. This is a 2012 Eco manual, all stock. A/C off, about 62 degrees outside, and engine fully warmed. It hovered at 60-61mpg average over this 8 mile stretch. The average speed was pinned at 55.3mph until I shut off the cruise and took this pic. I think the sweet spot for MPG is between 50 and 55mph. I'm impressed!