This question may enter the realm of gamification quickly with vehicles such as the Volt that have on-demand access to more than one fuel source.
Consider this: when driving a Volt down a mountain, favorable conditions may enable the downhill regeneration to create enough electricity to both power the car and recharge the battery with sufficient power to use to drive for several miles after reaching level terrain. Those distances are thus fueled by neither gas nor grid electricity. If your battery still has some grid power as you arrive at the top of the hill, you can choose whether you want those regen-powered distances to count as Electric Miles or as Gas Miles.
By switching into Hold mode at the top of the hill (if you’re not already in Hold), your battery’s state of charge doesn’t drop back to the Hold set point level until after you’ve driven those several miles at the bottom of the hill. That total regen-powered distance increases your Total Gas Miles without increasing Total Gas Used, thus increasing your MPGcs (gas mileage when using gas).
By remaining in Normal (or switching back to it from Hold) before heading downhill, the kWh Used will decrease as you head downhill (net kWh Used = +regen added - grid power used). Once you reach level ground, you continue in Electric Mode. Now the kWh Used will again increase, eventually returning to where it was at the top of the hill. At that point, you’ve added that downhill plus regen distance to your Total Electric Miles without increasing Total kWh Used, thus increasing your potential AER (and miles/kWh average).
Choosing Hold before heading down a long hill results in higher MPGcs and lower AER. Choosing Normal results in lower MPGcs and higher AER. Neither choice affects the trip MPG.
Consider this: when driving a Volt down a mountain, favorable conditions may enable the downhill regeneration to create enough electricity to both power the car and recharge the battery with sufficient power to use to drive for several miles after reaching level terrain. Those distances are thus fueled by neither gas nor grid electricity. If your battery still has some grid power as you arrive at the top of the hill, you can choose whether you want those regen-powered distances to count as Electric Miles or as Gas Miles.
By switching into Hold mode at the top of the hill (if you’re not already in Hold), your battery’s state of charge doesn’t drop back to the Hold set point level until after you’ve driven those several miles at the bottom of the hill. That total regen-powered distance increases your Total Gas Miles without increasing Total Gas Used, thus increasing your MPGcs (gas mileage when using gas).
By remaining in Normal (or switching back to it from Hold) before heading downhill, the kWh Used will decrease as you head downhill (net kWh Used = +regen added - grid power used). Once you reach level ground, you continue in Electric Mode. Now the kWh Used will again increase, eventually returning to where it was at the top of the hill. At that point, you’ve added that downhill plus regen distance to your Total Electric Miles without increasing Total kWh Used, thus increasing your potential AER (and miles/kWh average).
Choosing Hold before heading down a long hill results in higher MPGcs and lower AER. Choosing Normal results in lower MPGcs and higher AER. Neither choice affects the trip MPG.
