I don't think it's measuring lifetime. My last tank refill was around 61MPGs in a brutal heat wave. I haven't reset it though in months, if ever. I believe I'll get a 700 mile tank once the weather cools. Or maybe in the spring after I've broken it in a bit more. It truly is an engineering marvel. But don't expect the Prime to get anywhere close to the LE in hybrid mode.
Total measures lifetime from whenever you manually reset it. If you haven't reset it(pushed and held the OK button while on the Total screen) since you took possession, then that's your average over however many miles you've got on the car right now.
That's what I figured. Toyota isn't always good at user-friendliness. On Gen 4, the trip button on the steering wheel toggles it.
All the MPG gauges have been very accurate for me. But I don't know what this "total average" is measuring. It can't be lifetime.
It's what the manual says: Average fuel economy: Displays the average fuel economy since the function was reset, (Total) the average fuel economy after starting, (Trip) or refueling. (Tank) Are you sure you didn't reset the function at some point? You could always reset it again at the next fill-up and restart your calculations from there.
I am guessing that the tank average could be somehow accurate, but the trip average and total average are overstated/overestimated by perhaps as much as 15 mpg, which makes these averages useless to look at. It could be a fault in the algorithm. What are your manually calculated tank averages for your tanks to date? You must have only about three tanks so far.
Toyota really burried the mpg and other eco stuff in Gen5. I had both a Gen 2 and Gen 4 cars. On those, there was a single odometer, which you cycled what was viewed via a button on the steering wheel. In order, the possibilities were: 1) Total Mileage 2) User settable odometer A--I reset this when I filled the tank at a gas station 3) User settable odometer B--I usually used this for trips with multiple stops 4) Current trip (reset every time you powered off) 5) Distance to empty 6) Blank For 1) through 4), the displayed MPG would correspond to that odometer. In Gen 5, they've blown this up. There are still A and B odometers, but no MPG display corresponds to them. The distance to empty is permanently displayed. The odometer cycle button is now behind the steering wheel next to the instrument panel light control. The cycle is now Total Lifetime Mileage, User A, User B, and distance until required maintenance. There are now 3 fuel economy views, which can be in MPG, km/l, or l/ 100km) You can view either trip economy, tank economy, or lifetime fuel economy, but you can't easily switch between these on the fly. It requires going to the Vehicle Setting Menu, selecting Fuel Economy, and then selecting the view you want. The mileage graph for the last 'n' minutes, rather than being an option you can quickly flip to in the fuel economy section of the multi-information display, is now a selection on the multimedia screen. So, viewing that requires a decent amount of attention rather than a no-look tap on steering wheel buttons. I'm still trying to figure out when history is saved and when it isn't.
I haven't had that menu up since I first bought the car. I may have reset it then. But there would have only been a few hundred miles on it.
My last one was like 61 MPGs. The others were slightly lower. I've idled my car a lot in the heat with my dog in it. AC most of the time.
Alright, so, the total mpg and trip mpg are overstated/overestimated by almost 20 mpg, and the tank average is overstated/overestimated by almost 10 mpg, which makes these display readings useless. I thought the 5-mpg overestimation in my Gen 4 Prius Prime was bad. Good job, Toyota!
You said that your lifetime manually calculated tank average was ~ 60 mpg. Your car-calculated total average is off by 18 mpg, trip average is off by 24 mpg, and tank average is off by 8 mpg. Reason is restored after you finally stated your lifetime manually calculated tank average. Until then, it had all been surreal mpg values being talked about in this thread. So, you are getting 60 mpg, only 5% higher than the EPA combined city/highway value of 57 mpg—end of story.
This is definitely not true. See my post from the other thread. The last time I filled up. The tank average gauge read 61.5 and Fuelly showed 60. So if anything they improved their calculations.
It is clear that the total average and trip average are way off—by about 20 mpg. How does the car really calculate the tank average?? The fuel-level sensor in the tank is not only very imprecise, but the actual fuel level changes wildly with the ground slope. So, if the tank average and manually calculated average are agreeing, I consider that as good luck more than anything else. If the total and trip averages are so off, there is no reason to take the tank average seriously either, as they are calculated by the same algorithm. If the tank average is agreeing more with the manually calculated average, it is probably thanks to a systematic error in such as estimating the fuel level in the tank that effectively reduces the metered mpg by subtracting a systematic amount when the computer estimates the tank average.
