Hello All. VERY MUCH a newbie here. My question is, I picked up the 2010 Prius, and have been driving on the dealer fill up til today. The tank was down one bar below 1/2, so we filled it up. For the past several days we have been watching the Consumption display, and it was indicating that we were averaging about 50.2 mpg around town. This is great stuff to me btw. After the fill up today, the avg consumption display has gone nuts. it started out reading 99.9 mpg & is bouncing around all over the map. I also noticed that there appears to be 2 different avg consumption settings that I can click through. One reads lower avg mpg's than the other. I'm sure there is a logical explaination for this, although I can find nothing to explain it in the manual. Thoughts Anyone? Thanks, Phil Griffin
The average display that is jumping around resets when you fill up the tank. It is showing the MPG for your current tank of gas. If you coast out of the station it will read 99.9 MPG, if you then floor it up a hill it will drop precipitously. It will even out as you get more miles on the tank.
The automatic reset on fillup is a Gen2 thing. Gen3 resets are strictly manual. Otherwise, Corwyn is right. Momentary mpg varies wildly, so trip mpg will also vary wildly when the number of miles since reset is small. As for two different mpg readings, OP should note that there are two trip meters, TripA and TripB. Each needs to be reset separately, and it appears that you reset only one. That one will have the current tank mpg, the other will likely have the car's mpg either since someone at the dealer reset it, or if that didn't happen, since the car was built. I reset one meter every refill, the other every day. The daily meter provides much faster and more detailed feedback about driving for efficiency. And with the cold engine in the morning, its initial value is horribly low, but climbs as the engine warms and the miles roll up.
Thank you guys. We put about 13 miles on it yesterday after the fillup, & it did come down from the 80+ mpg to about 60 something. So it looks like we're heading back closer to where it was prior to the fill-up. How many mile should I expect to have to put on it before it's reading accurately?
It never reads accurately. My MID is ~7% optimistic. Another rough estimate is to take the distance driven + MTE (Miles To Empty) then divide by 10. From another point of view, the wild swings are accurate. Drive 1 mile on battery the MPG is infinite. Then drive 50 miles burning 1 gallon. The average is now 51mpg. Around half a tank there is enough history so that large changes for short distances don't have much effect.
As already mentioned, the trip MPG readout stabilizes over distance. I usually have a high initial tank MPG because the car was warmed up before I filled up at the gas station.
As others pointed out, it is not inaccurate now, other than the normal built-in error (6% in mine). If after leaving a gas station with a warm engine, you travel home at moderate speeds, downhill, the displayed mpg can be sky high. Because it really is. But returning uphill the next morning in bad traffic, starting with a cold engine, the trip mpg meter will likely plummet down to 'normal'. Even small elevation changes can have a large impact on Prius mpg, so round trip numbers are much more meaningful than one-way results. And at least one of these directions should be starting with a dead cold engine.
Performed a little test yesterday. With engine warmed up, reset the "B" trip, drove home from the barn (country road, 5.1 mi) and registered 61.8 mpg. Then this morning from a cold start (overnight 55 deg), reset "B" trip and drove 3.1 mi stop and go in town, and registered 39.4 mpg. Not too scientific, but gives one an idea of what you can see. I always keep "A" trip to give me mpg and miles between fillups (normally between 9.5 and 10.5 gallons). Most of my dailly trips are between 5 and 15 miles. Keep the tires at recommended levels.
