Interesting observation

Welcome to the wacky world of the Prius! Do a search on "guess gage" in the forum and you will see how it earned its name.

 

Any difference in elevation?

Tom

 

Using the mfd numbers, you burned 4.8 gallons and 3.75 gallons on the two legs. My guess is that you put in more than 4.8 gallons before the final leg. This means that you started with a fuller tank on that leg which is consistant with with the greater distance travled before losing the first pip. That is the second element in the equation (unsolvable). Not only is the fuel gage inaccurate but most of us find that fillups are inconsistant due to the nature of the fuel bladder system.

 

pips in NO way accurately represent an equal portion of gas in the tank...........it drove me nuts for while as well. Now I just drive........

:car:

 

The same is true of the gas gauge in a "normal" car: the scale is NOT linear. You can burn 3-4 gallons before the needle moves off full, then the needle moves quickly to 1/4 full (representing 3-4 gallons) then the needle crawls to empty (the final 4 gallons, assuming a 12 gallon tank. Similar proportions for any other size tank). I think the Prius gauge is designed to mimic the behavior of a needle gauge in a standard car.

What I find helpful is the MPH readout and miles on the current tank. With those 2 numbers, you can pretty accurately decide how many miles you have left before you simply have to get gas. (As long as you only count on 10 usable gallons in the tank at the start; less in winter weather...).

BTW: Here in San Jose, I filled my Prius on a very hot day (100F), just after the second to last pip blinked out. I put over 10 gallons in, the first time that's ever happened. So I'm betting that I got more in that time than I had burned off going about 470 miles (with MPG reading right at 50). I estimate that I had a whole gallon extra in the tank (12.9 rather than 11.9, that is). I expect I'll get almost 200 miles before the top pip disappears.

 

I've seen my mileage range from 46-56 MPG on my most common long highway trip, depending on the weather, wind, tire inflation, oil level, and the amount of wax on my car. Usually, the mileage fits within the smaller range of 47-51 MPG.

Sometimes, I think the gasoline brand and type (plain vs. 10% ethanol) makes a big difference, but it is hard to tell, even after 125,000 miles.

 

more reason to fill to the first click and rely on the MFD. or your SGII.

That fuel bag really makes me wonder who's idea that was. and if he was getting even with us for something or just enjoying a joke.

 

Yep just drive.. do no other calculations and just enjoy the vehicle. At each fill up note the gallons pumped and the miles driven since last filling. Then add these figuers to a spreadsheet or GreenHybrid database and after a year or two you will have a good accurate view of your realworld fuel economy.

The only valid consideration to be of any concern is
Total Miles Driven / Total Gallons Pumped = Avg MPG.
However I still prefer
Total Gallons Pumped * 100 / Total Miles Driven = Avg GPC