How to determine average mpg

I still do it the old fashioned way in my non-Prius cars...Fill up the car and do not put any more in when it clicks off, then take the miles driven and divide by gallons. I ALWAYS have done this...not forgetting to reset the trip odometer...poor mpg on one of my cars a few years ago came down to a bad 02 sensor. The seemed to drive just fine except for the mpg drop. But, I'm sure you know the old way.

 

In my 2013 (not sure of the 2015), you can put the odometer in Trip A rather than total miles (Odo) and it will keep a running total of miles driven, avg economy (mpg) and avg speed (MPH). If you reset the Trip A after a fill-up, it will accumulate the miles and mpg for that tank. When you power down, the display shows total miles (odo) along with data for the current trip (miles, mpg, speed, fuel used/cost) briefly before shutting off.

 

Does your model NOT show a MPG figure with each of the trip ODO displays ??
Have you actually read the owner's manual yet ? If not, you should.

The ONLY way to get an accurate MPG figure is to divide the miles driven by the amount of gas used.
None of the onboard calculations are really that accurate.

 

Not sure with the 2015, but with mine: on the steering wheel buttons, push Trip first, then Display to cycle through the options. Per FuelMiser, set it to Trip A, or B.



And yeah, it's inaccurate, take it with a grain of salt. Calculate as well if you want to accurately track how your doing.

FWIW, I typically record the odometer reading at each fillup, rather than Trip A (or B). I do reset the trip meter at each fillup also, but just for insurance, and feedback as we're going through the tank. Any time you shut the car down, regardless of what's displayed, the odometer reading will display for about 30 seconds.

 

There's a difference between Prius MPG and real world MPG.

If you want PRIUS MPG, I believe all you have to do is use the MDF trip "A" (or B) function and it keeps a running average of what the car measures for efficiency until you mash the reset button, and then it starts all over again.

Of course.....if you want the truth (Prius MDF efficiencies are as accurate as the DTE readings.....) then you'll need to reset the trip odometer when you fill the car and hand calculate the next time you fill the car.

If all of this is too involved for you you can try an app like Fuelly.

RTFM
Read the....er....FACTORY manual.

 

I don't think the Prius mpg display is inaccurate, that's too kind. I'm finding a very reliable positive bias, around 7% on average, with variations likely due to vagaries in pump shut-off.

 

Good point!
I stand corrected.

 

I just performed my second fill-up today since buying my 2013, and upon restarting the car and pressing the Trip button to reset Trip A to zero, it briefly showed the fuel cost setting giving me an opportunity to change to the price I just paid! Since I was not prepared to see that, it disappeared before I could react and I had to set the fuel price the normal way--press Disp until you get to Settings, etc. I hope I did not misinterpret what I saw, and will try and remember it next fill-up. PS: I calculated my actual fuel consumption as miles traveled over gallons consumed, and the Trip computer turned out to be about 5% generous. I computed 47.5 mpg and the car was showing 50.1 mpg.

 

In my experience, typical of ALL on-board fuel calculations: Chevy Malibu, Hyundai Elantra, Ford Fusion Hybrid and Prius C.

 

Honda Civic Hybrid had very honest mpg display. Erred slightly on conservative side. Of course their claims and expectations for the car were something else.

 

Honda's hybrids are a joke TBH...

 

It's still a rolling joke, but yeah, the IMA system on our 06 was under-designed. It's still in the family, on it's second battery (Honda sprung for gratis replacement out of warranty, which was good), but that new battery is also ailing. Over 230K km's now.

Their new Accord Hybrids appear to be taking a lot of cues from Toyota, but I'd still wait-and-see. Besides, I'm kinda hooked-on-hatchbacks now.

To paraphrase the Wizard of Oz, our poor '06 Civic Hybrid is a bit of a "clinking, clanking, collection of junk now".

 

True. I totally agree.