I've noticed that even in gear with my foot off the gas pedal, it still never shows less than 0.2 GPH (gallons per hour), but I could swear Hondas shut the injectors off entirely whenever you're in gear, off the gas pedal, and above 1200rpm or something. Maybe switch yours to show GPH and see if it still shows a significant GPH reading, because of all cars, the hybrids should be the ones most likely to have a zero GPH reading when coasting down from 40+miles per hour.