As an aftermarket plug in insight owner I choose to abuse the undocumented "ev" mode to coast longer once accelerated to speed by the mix of the two per the onboard computer. Of course having a higher state of charge the system automatically mixes in more electrical power or assist than it would otherwise. The limit is similar to the prius 2/3 in the fact its only under light throttle, otherwise the ice kicks back on and both are used.
I imagine having the plug in ability may cause a skew in mpg from the drivers stand point trying to conserve the energy since its limited or use more of the ev feature.
Then of course you got the other fact most hybrids give best fuel economy when you use the least of the electric as possible.
I like the fact I can keep up with traffic never exceeding 80 mph and still clocking 54 mpg on the mid.
