It might be my imagination, but it seems like on warm, humid days (temp over 65, dew point mid 60s or higher), the insight just wants to take off. I can park the instantaneous MPG at 75 and still be picking up speed. Drop the temperature and humidity, and I can't maintain 55 at 75 mpg on the same roads. It doesn't seem like there is enough of a difference in air density (i.e., air density is proportional to temp in degrees kelvin other factors being equal and water vapor is lighter than dry air) to account for this. Anyone else notice this or have an explanation?