There are times when I'm driving slow and "under load" or accelerating that the FE gage shows in the 20 to 30 range and the ICE is charging the battery. Letting off and reapplying the throttle won't kick in the battery mode and I just go back to the 20-30 range. It does not last all that long though (a couple of miles). When the battery is charged adequately I can let off and reapply the throttle and go to E mode. When I'm at speed (say 50 or 55) and there is excess horsepower, the ICE is sometimes still charging the battery, but it's with excess (normally wasted) horsepower and I get in the 50 to 60 mpg range.