what's the most accurate way to determine MPG ?

i think you're only guessing until you fill up. and even then, you need a few tanks to average because you can never fill up to the exact same point every time.

 

I'm guessing that every one of the displayed numbers are based on the same fuel consumed measurement based on drops of fuel consumed. How would it be any different?

Mike

 

I bought a scangauge e from amazon. It is very accurate.

 

Agreed that the fillup is the best way to calibrate. I just filled the car up for the first time (it came with only 2 gals because of truck transport, so this is not my true first fillup) and I noticed that the fuel gauge went down one square after about 45 miles, half of which were EV. This seems odd but at least the mpg indicator tells me that I am doing much better. Typically in Prius (e.g., my 2005) the first square would not disappear until 100 miles sometimes. So it seems that the fuel gauge continues to be highly nonlinear, though now it is in the other direction.

One does wonder why technology is not used that tells exactly the fuel content of the tank. It can't be that hard....

 

Truck transport?

 

Both range (EV and total range) gauges are just estimates and can vary quite a bit. Miles traveled on the odometer is very accurate. The trip summary screen can vary a bit bit doesn't affect the odometer so always go by the odometer reading when in doubt.

 

Maybe an out-of-state purchase?

 

He said he had 2 gallons left after truck transport. 8 gallons were burned on the transport?

 

The range readout is an estimate based on your current mpg. I've driven up to 25 miles with it reading zero. You can't rely on it for consumption calculations. Use the EV Ratio screen. It's only accurate to the gallon (no decimals, it always rounds down) so it's not too useful to you until you've used a lot of gas or you can do error bars in your calculations.

I've never reset either of my EV ratio screens and they currently read 153 gallons. So I've used between 153-154 gallons for the distance shown on my odometer.

 

El Dobro: Yes, it was an out-state purchase. Plug-in not available in Colo so I had it trucked from a dealer in Seattle and am happy with how it worked out. Dealer said that when vehicle is transported by truck they are asked to not fill it up. So I got it with 2 gallons, not a full tank.

The range indicator seems odd. Right now on current tank it says I have done 90 mpg so for on the tank (I use trip A for that), but my range-to-fillup is given as 480 miles, well under 10 x 90. So range must be based on the assumption that there will be no more EV use. Makes sense for highway driving, but that's about it.

My goal is to get through to my first fillup with 1000 miles, but the darn "start-on-hill" issue might make that tough. I guess to get that I have to get 50% of my miles to be EV.

 

Your total range estimate will be whatever EV range you have (at the time you're looking at the total range number), plus whatever the car estimates you'll be able to drive (on gas only) considering the amount of gas left in the tank.

If you have 10 gallons in the tank and you've been averaging 48 MPG (on gas only) and have a full charge indicating 12 EV miles, the car's total range would show 10 gallons x 48MPG + 12 EV miles= 492 miles total range.

Like you said, it would make sense for highway driving.. or more specifically, it would make sense assuming you're not going to charge the car, since the car has no way of knowing when you plan to charge and how often.

 

Yes, of course that makes perfect sense for the Range indicator.

 

A picture is worth a thousand words. I'm sure someone will be able to answer your discrepancy when you take a picture of your EV Ratio. Make sure you have the ODO displayed at the same time.

 

According to your pic, you traveled 147 HV miles on 4 gallons of fuel for 36 mpg. Pretty terrible but I assume it's because you idled most of it away as you have an extremely high EV ratio. 212 miles for 6 gallons of fuel would be 35 mpg so both numbers are on target.

3 bars should be about 3 gallons. You should show 3 or 4 bars right now if everything is correct. Each bar is a little under a gallon for the PiP. I just filled up 8 empty bars with a little over 7 gallons of gas. So pending a picture assesment, either there is something wrong with your car or someone is adding gas into your tank to play a joke on you.
The Fiat Mileage Prank | Car Talk

 

If you can find out the average inaccuracy for PIP, just adjust what the car's telling you by that factor.

In my case with 3rd gen reg Prius, the average error with about 2.5 years of calculation is 8%. I've heard the PIP error is less though.