Actual Gas Mileage Trip meter vs info screen

Yup

Once you've filled up, reset the trip meter, and for a more bullet-proof method, record the odometer reading (miles since new). Go through a tank, refill, check and reset the tripmeter (and or note the increase in odometer).

Then divide the gallons of gas you put in by the distance travelled.

Repeat this for a few more tanks and any errors introduced by variations in fillup will cancel out.

 

welcome to priuschat! there's no way half a tank is 6 gallons. you need to do what mendel recommends, not panic after guessing how much gas you've used. if your screen reads 52, you're probably getting around 48 or so. all the best!

 

That is not how the fuel gauge reads. A few of those gallons are hidden below the last mark.

How many gallons did the fuel pump say you put in? If you didn't look the reading on the pump or the receipt, then you CANNOT compute actual mpg.

 

It's not easy to fill the tank completely, partly due to the quirky variable capacity bladder. I've never put more than 9.975 gallons into my Prius in my 8 years of ownership.

Yes, reset the trip odometer, drive until you're nearly empty (say 2 pips, so that you have a reasonble cushion) and make a note of how many gallons you put in at that point. Calculate miles driven / gallons added to take you to "full". You'll need to average this over many tankfuls to get a reasonably accurate number, as some will be way higher than the MFD and some will be way lower..

You may as well average the MFD values as well.

 

You can't go by your first fill-up. It sounds like your trip meter and your info screen were not in sync with each other, but they should be now if you reset both at the fill-up. Let us know what your results are on the next fill-up.

 

Don't forget to add your location to your info.

 

Again, the trip meter can trip you up, lol. The deadliest method to record distance travelled between fillups is by recording the odometer reading, subtracting the latest from the previous. Print out your gas receipt, write the the odometer reading on it, you're good to go.

At least on our 3rd gen, every time the car's shut down, the odometer value is displayed for close to a minute.

 

see what happens in the next few days and report back here. if no improvement, ignore advice and take to dealer for analysis and repair. are you under the 10 year 150,000 mile warranty?

 

In that case, you have absolutely no basis for figuring MPG other than what the info screen says. Period.

The fuel gauge is a cheap crude device to keep you from running out of fuel. The top of the gauge is not at the real top of the tank, the bottom of the gauge is not at the real bottom of the tank, and the marks in between are not necessarily linear, or consistent from car to car or even tank to tank in the same car.

If you desire an independent check on the displayed MPG -- a good idea, as those are known to shade the truth -- then you must keep track of the actual amount of fuel pumped into car. For ordinary people without a lab full of test equipment, there is no other way.

FWIW, your model year suggests that the MPG display should be quite good. Starting with the 2010 models, they became significantly 'optimistic'.

 

Now, it's called the "feel good" readout.

 

Yeah..I figured that out. It is to the tune of 10% or so.

 

I use an app called Road Trip to track mileage and fuel expenses. It also allows you to record your own economy data, ave speed, temp. It gives you an idea of how much the display is off by. My actual calculated is about 1.6 - 2 mpg variance from the display.

 

I just use Fuelly (as you do I see). I don't trust the trip computers. They are nice for a general idea of instataneous MPG, but long haul they are not smart enough to know you are coasting and just see it as you are getting 99+ MPG.