Actual MPG vs. car's estimate, informative?

slightly useful, but I prefer long term averaging. when we go to Florida, there's quite a variation in each tank based on weather and driving conditions.
after the 4,000 miles or so trip, I'm comfortable with the average.
for a one tank trip, that fill up calculation is close enough for me. with a gen 2, you can usually get a good feel for the bladder with experience, and if it is filling to different levels at different times.

 

By law; those numbers need to fall within + or -, 5%-10% of specifications, though most OEM will "juice" the numbers to land on the higher end of the standardized test. Their way of gaming the system. The same way OEM's claim their ATF is life-time; will last to the end of their warranty period.
I would trust a year long average of fill up tanks calculation averages over the built-in guess-o-meters. Luckily the MTE calculations are very pessimistic; as it should be.

YMMV

 

By law? What law? I remain unaware of any legal regulation of MPG display accuracy.

The accuracy of the EPA MPG estimates displayed on the Monroney window stickers are regulated. But this does not carry over to the dashboard MPG indicators.

 

I'm talking about the speedometer, you know one of the data points used to determine mpg. Other data points can also be manipulated to skew the results the testers want. Again; long term averages would get you a better picture of your own personnel driving style and commute parameters.

 

My best tanks when my Prius was new were between 55-59mpg average by the computer. They say the Pruis gen 4 tank is 11.3 gallons. I think the most I have put in my tank was 10.6 or 10.8 gallons but typically 9.6-9.8 gallons is what the pump shows when filled to the shutoff.

I think the only way to truly measure your fuel economy would be to siphon your tank empty. Then measure 5 gallons and run the tank dry. I am not going to do that but others may want to give it try. Pump errors or outright theft at the pump can give you inaccurate measurements. There are a lot of people who put in 5 gallons and assume a lot of things when measuring fuel economy. Like they trust the pump and gas station owner too much. Or they assume how much fuel is in their Prius tank. The true size of the Prius fuel tank has been questioned for years.

I put in a new 12V AGM battery in my Prius. My city fuel economy went up substantially. Highway fuel economy seems stable. My current tank is showing 52.1MPG. I will be putting in spring/summer blended gas shortly. It may be the same gas/ethanol mix as my last tank.

If it were like new my Prius would get 55-57MPG without much effort. If I did more highway driving my fuel economy would be higher. A lot of my driving has been 2-3 miles. The Pruis does not like short trips for fuel economy. So 52MPG is pretty good for a 2017.

 

Neither you or pasadena_commut made any mention of the speedometer.

And no, the speedometer is not part of the MPG calculation. The odometer is part of the calculation, but it is not regulated by law, only by product liability and defect lawsuits.

Do remember that the manufacturer-intentional built-in speedometer and odometer biases are separate and different.

 

... which was the whole point of the above reply string.