My commute one way is Hybrid perfect. Night time, no traffic, some up hill and some down hill (more down hill). I activate the DCC at 62 mph and with no interactions with other traffic... smooth sailing! Now for the issue: With the same exact driving conditions with temperature within 1 degree F I am experiencing a fluctuation in mpg from 64 mpg to 75 mpg. That is ALMOST 20%. I can tell when the car is going to get the good gas mileage because the engine will be "stronger" and the exhaust tone is more noticeable. I took the car in for it's 5,000 mile service today and explained the issue. Of course, they find no computer codes and can find nothing wrong. This is my THIRD Prius and I understand battery charge can have an effect but that should not account for 20%. Any ideas? Thanks!