The leaf cars only show regenerative braking and not recharge by the engine so i'm not sure how you're getting regen on the highway unless you are braking or even just coasting (1 min consumption screen will show 30kWh leaf cars while the 5 min cons. shows 50kWh per leaf car so keep in mind that the numbers the leaf car represents changes depending on which Cons. screen you're on).I have recorded & computed my mileage for every tank full for every car that I have ever owned. For my 07 Prius, I've averaged 49.1 mpg (computed), with a low of 32.2 and a high of 69.1 for a single tank of fuel, since mile1. The computed average of the displayed mpg is 50.5.
I'm not sure that "green leaf cars" (I think they look like little green turtles) necessarily indicate too much braking. Recharging also occurs w/o braking. Last week (after my 50K service, so everything was "in order") I noticed 5 "green cars" in a 25 minute span (5 min screen) while driving about 20 miles on a 2 lane rural state highway with very little braking. There were maybe 3 traffic lights (& very little traffic) during that time. A couple of days later there were 3 "cars" within 20 minutes while driving on an Interstate highway.
I suggest that you hit "reset" on the display when you fill up your fuel tank. That will reset both the mileage and mpg. I "think" that the mpg displayed keeps computing (from last reset). I also "think" that my mileage auto-resets after fueling . . . I always reset, so I don't remember. It takes very high mpg (over several tank fulls) to make even a slight increase in the average when the computation is spread over 10,000 miles. Maybe you just need to restart your calculations.:Bruce: