For me ECO mode still trumps the flash for fuel economy on the super slab, but not by much. On the way to and from the National, I alternated each tank full, only on the super slab, running ECO mode and the standard mode with the flash. ECO mode did better by ~2 mpg. That being said, I did not purchase the flash for the fuel economy and I am quite pleased with the "ride-ability" improvements from the flash. I still wouldn't mind getting the 48-52 mpg others have mentioned? I reset my avg mpg on the display when I got the flash and it is currently displaying 42.3 mpg, which is a little optimistic when compared to hand calculations, and about the same readout as what I had before the flash.