I am finding the car is about 2 mpg more optimistic than reality

sounds about right.

 

Lots of data. Just poke around.

 

Good stats...but silver not gold we have to say nate

 

I accurately monitor the amount of gas put in the tank, and the number of miles driven, and simple mathematics gives me the most accurate fuel consumption. My 2009 Gen II Prius has a flexible bladder which can confuse the figures if looking at individual fill-ups (ambient temperature, time of year (seasonal variations of gas chemistry)) but over a long period of time, you can't beat my simple mathematical method (…but, as they say YMMV! ) IMNSHO, your 2 mpg difference is just noise!

 

Agree that +2mpg of optimism is about right for most Prii. I have kept an extensive fuel log since tank #1 on the GenIII and it is always that way, from any tank. Nothing seems to have changed the way Toyota does their math. Oh well.

 

Consistent 5% error in my 3rd-generation. A 2016 should be better.

 

My Gen3 is 6% optimistic (lifetime average) - I calculated that after the 3rd stop of the nozzle. Otherwise more towards 5% when calculated against the 1st nozzle stop while re-fueling.

 

mine is more real than reality

 

Could you please express the difference between "calculated" and "displayed" as a percentage, because the differences are probably proportional to the MPG you are getting?
Also, people need to include what they mean by "calculated". There are reports here that the odometer reads low by 1-3% versus GPS tracking. I'm still gathering data, but my Gen 4 seems to read 1% to 1.5% low. For our hand calculations we're stuck with using the number from the gas pump as the volume of fuel. Filling it to the first click with the automatic shutoff (if there is one) on the slowest flow setting may at least reduce variations.

 

Our 2010 Prius is always off by about 6% - 6.5 % mpg than the displayed on the dash mpg. Calculated is miles driven divided by gallons used derived from the gas pump with a full tank. Here is an example. Displayed mpg is 55 on the dash. Calculated, miles driven divided by gallons will be somewhere around 51-52 mpg, not 55 mpg as displayed on the dash....

 

By "miles driven" you mean "miles shown on the odometer"?
The displayed MPG in my 2011 Gen 3 was usually around 5% higher than the "miles shown on the odometer". I regret that I did not use "miles covered according to GPS": that would have reduced the apparent error. I've been using a free app called SpeedTracker on my iPhone and it's very easy to use as an odometer.

 

Actually is not easy at all to calculate the fuel consumption - for the car and for the user.
Things like:

1. how much did you think you put into the tank and how much did it actually go there? (i.e. how much is the gas station effectively stealing from you?)
2. did you fuel up in winter or summer (different fuel volume change)?
3. did you stop at the 1st, second or third nozzle stop?
4. does the nozzle stop the first time always at the same level in the tank? will be affected by foam (if any?) of the fuel while being flushed possibly quite fast in the tank? and any air bubble that did not manage to come out, has made the nozzle stop beforehand?
5. did you calculate the distance (as mentioned above) shown by the odometer? how precise is that? did you do that with winter or summer tires on? (I have a difference of 300m or more, over a trip of 17km, depending on whether I used the summer or winter tires)

I know that cars as well sort of estimate fuel consumption, but are in fact more precise that one might think. I remember seeing a post either here, on some other website talking about this precisely.
So, I think one can calculate only so precisely how much the car actually consumes.

For me, as long as the difference between calculated and displayed is averaged over a few weeks/months, and the % delta between and shown is reasonable and constant (e.g. 6% with changes around 1%), it should be ok. And I more sure the changes in displayed vs calculated are due to gas station cheating and temperature changes, than the Prius having something wrong.

It is in fact more disturbing to see claims of xL/100km (e.g. 4L/100km) consumption based on the EU cycle and then you get x+3L/100km (7L/100km).

 

Just downloaded it. Thanks!

 

With well over 100 fillups on a third gen, my average error compared to dash display is 7.5%

 

When I bought "The White Knight" I didn't have any big expectations. I told myself I would be perfectly happy with "only" 45 mpg. That's still way better than any other car I ever owned; And it's better than 98% of other cars on the road.

I never thought I would be averaging a nice steady 60 mpg! At last fill-up, my hand calculation was the same as the dashboard display. I drive my Prius like any other car. I don't do anything special. (I even have the AC running constantly) I'm amazed at the outstanding gas mileage!

Thank you Toyota! And thank you Toyo Tires!

(Edit to add: I usually keep the car in "Eco" mode. But I'm not light-footed.)

 

Perhaps those of you who agonize about distance, might be advised to get one of these and bolt it on to the rear-bumper:

 

I hate u.

 

I don't know how accurate it is. The light blinks often, not sure if that means it is taking a data point.

 

I bought the SpeedTracker app for my iPhone. This morning my everyday 28.9 drive into work was measured by SpeedTracker as 29.3 miles. A difference of .4 miles. Or 1.4%. Since neither the odometer or the app has actually been calibrated, I do not have enough data to make a determination as to which is more likely to be correct.