How does the average mpg work?

only for this tank, no it automatically resets when ever you add more than 4 gallons. Life time only on your spreadsheet.

 

it would only mess up your reading for the previous tank. I mean it would be for a tank and a half. Not really messed up

 

Ohh, I've been around, a LOT.

Not sure exactly if there is some kind of sensor or somehitng else that resets the MPG, but I know that it doesn't reset right away when you pass the 4 gallon mark. It resets iteself after you drive a mile or so.

 

I am convinced that the '06 DOES NOT reset the average MPG indicator when you fill up. That is based upon my car, a friend who also has an '06, and experience with an '05. There is definitely a change. I believe if you don't touch the reset button, you are getting a lifetime mpg average but the miles indicated are for the tank.

Example: A few days ago I put 8.9 gallons in my 2006. The miles indicator on the consumption screen reset to 0 in 100 to 200 yards. My mileage was 39.8 MPG before fillup. It stayed at 39.8 for miles. In a 7 mile drive home, starting with the car warm after getting gas, I had only 50+ MPG segments showing in the display. The mpg average indicator only went to 40.1 mpg. Now being an engineer I calculated that (39.8*361 + 55*7)/368 = 40.1 (I had 361 miles on the car when I filled it).

This is verified by my friend at work with 1200+ miles and 4 fillups. And when I drive Barbara's 2005 Prius shortly after she fills it, I see an average mpg indicator that changes around a lot as the engine goes from cold to warm or as you go up and down hills. My 2006 (with 60 miles now on that tank) has been rock steady with miles of driving (cold, hot, high mileage, low mileage) needed to budge the average mpg indicator by .1 mpg. So it acts as if it is averaging against the 400+ miles on the car rather than the 60 on the tank.

I had been driving an Audi with an average mpg indicator for 5 years before this one. I know what to expect. There is a change from the 2005 and it is not mentioned in the manual. My car is an 11/05 build date.

- Tom

 

ok it's starting to look like Toyota went back to the cumulative MPG readout on the 2k6 from all reports. The Classics were cumulative and the 2k4-5's weren't. So I stand corrected on this. Don't tell the wife she'll want a new one.

 

Only the "Average MPG" does not reset. The "miles" next to it resets after a few hundred yards of driving. I wonder what genius came up with that one? I suspect it is not an intentional change as the manual does not say anything different than the 04-05's.

- Tom

 

Ok I know this is slightly off topic . . . but I have a 2005 and the first few times filled it it reset automatically. Miles and MPGs to 0. However, it has't reset automatically for several months. If I don't hit reset, it just keeps adding to the last tank. Anyone else experience this? Incidentally I allways fill up to a full tank, and usually when I have 1 or 2 bars left. I usually put in between 8 and 9 gallons.

 

why would it not know??? that is a very strange question.

if you are worried about it, you can manually reset it yourself using reset on the comsumption screen. if you do plan to track your lifetime (LT) mileage, (it is highly recommended) you should use one of the trip computers since it provides accuracy in 10ths.

also my reasoning why you should reset on every fillup. it would be impossible to track incremental mileage data. actually, not impossible, but very inaccurate. by resetting your mileage on every tank, its easy to calculate your mileage for short durations. eventually, the LT mileage indicator will be useless. it will move so slowly that it will no longer be a good inidicator of whether the Prius has changed its performance level

 

i also did not know about the mpg's now being LT or whenever you reset it on the 06's. i think this is a bad idea. having the mileage reset on every tank full is the way to go. this enables you to compare mileage from tank to tank. LT readings would eventually become useless except over a large range of time. if something is going on with my Prius that is lowering the mileage, i want to know about it as quickly as possible. i never wait for my tank to reset, i just manually reset it the same time i reset my trip meter when i get gas

 

I am wondering about this - I have now filled up Twice ( average mpg of 2 fillups was 42mpg - but it has been in the 40's here in Kansas City ) When I put in gas and the car resets ( 1st time it reset after about 1 tire rotation, tne 2nd time did not fill up until a full mile was driven ). When it "resets" the miliage goes to zero, but the mpg remains at it's last reading - if the mpg is just for this tank, then the mpg should reset to zero as well??

 

EDIT: because I broke that rule about responding before reading all the other answers first.

I'm mad! I wish I hadn't hit the reset button at the first fillup. Guess it's better than having it accidentally reset many miles down the road. And like y'all said, it's not like lifetime MPG is anything more than a novelty after a while anyway.