Hi all, Does anyone have any input on how the "miles to empty" reading on the dashboard is calculated? Specifically, how the battery affects this calculation? If the Prius were a non-hybrid, obviously it would solely be a calculated distance based off current fuel tank quantity, and an average fuel consumption and speed over a range of time (easy enough), but how would one factor in the battery?
It's based on your previous tank and it's the distance to your low fuel light (you have about a 10 litre reserve after the light comes on). It's calculated the same way as a regular car. The battery is not taken into account (if you're thinking about the extra 1-2km of battery power if the car runs out of fuel).
That may be true at the very start of a new tank, but after that I think it is recalculated in real-time based on your calculated MPG since the last fill-up. In other words, if you got 60MPG on your last tank, miles-to-empty might start around 600, but once your current tank is half-gone and you're only getting 40MPG, the miles-to-empty would be closer to 200 (rather than 300). Regarding the battery, it is not exactly included or excluded - the calcs appear to be based on your overall mpg since the last fill-up (which includes whatever improvement the battery has been providing, but not any specific # of miles you might be able to get from EV mode).
The one odd data point I can contribute here is that I was driving down to the States and wanted to fill up across the border, but was running really low, so I added 6 litres in Canada before driving to the States. The km to empty number did not reset at all! It just stayed the same. Does it require filling up the tank completely to go up? I imagine there is some threshold where it just doesn't recognize it should increase the number slightly? The fuel gauge did add an additional bar, so it knew it had more gas. Odd!
Good question - did you reset either tripmeters when you added fuel? I have been doing that every time I fill up (and I always fill to full, not partway), so I don't know exactly how miles-to-empty is tripped/reset... Two tests to do: 1) partial fill-up with tripmeter reset. 2) full fill-up with no tripmeter reset.
I did reset it. It still didn't trigger. Very odd! I watched carefully and it also didn't go down much during the drive to the States. (As if it was slowly figuring out that it had more than it thought originally!) When I filled the tank in the States it instantly jumped to the full normal range, even before resetting the trip measure. I'm a bit baffled and imagine there must be a minimum fill required to activate a recalculation, otherwise it just uses a smoothing formula.
