If you drive straight through
If you drive straight through, always keep it in Mountain Mode even if you charge it overnight. You do not have the HOLD option. This way you will always have enough power for hills and will get the best mileage. Mountain mode will automatically start the engine at about half the battery level (15 to 17 miles) and you will never have to make a decision when to use it on the fly. It will then drive hybrid style much like a Prius. Charging the battery by engine when it is depleted reduces the MPG to below 20 until the battery is at the proper level. Have a great time. Sorry to write so late.