At first I was using the nav system and the graphs to see if I can improve on my fuel economy. I've tried hard to do so for the first three weeks or so, but I couldn't get more than 35-36mpg regardless of what I tried (pretty much everything short of pushing my car). It started to become a frustrating experience so I finally decided not to pay any attention to the FE graphs and I used the nav system only for navigation or system energy flow occasionally (no graphs). I just wanted to see if I drive my car "normally" what do I get (my usual speeds about 5-10 miles above speed limit, no hard acceleration but not sluggish either etc). My mpg is currently 39.8 for my last tank and it was 40.1 on previous one (same roads as before, A/C on). I voted that it didn't make a difference for me (actually made it worse).