I have a question for all you longer term Prius owners . From what I read on PriusChat changing modes from Eco to Power to Normal only changes the mapping of the "gas pedal". If this is so , my question is does it really matter what mode you are in if you are using cruise control on a long trip, would all the modes get the same mileage? Arkie
Eco mode 'relaxes' the thermostat on the A/C, so it can vary more. This might help MPG most of the year in AR.
If you don't use the A/C, you should get the same MPG's from all 3 modes. ECO will improve mileage if you do use the A/C. It also helps with "feathering" the pedal for pulsing and gliding for those times you are in slow and go traffic.
