2023 Prime: Anyone Figured Out Tank Average MPG?

Unless the Tank Average measurement is totally hosed.

I drove three tanks with ----% on the guage at the start and end of each tank filling.
- Trip showed a reasonable MPG from Ready to shutdown.
- Total Average showed a reasonable MPG covering the multiple Ready to shutdown "trips" for the tank from filled to next filling.
- Tank Average (which does not have a "hold OK to reset") showed 99.9 MPG from the day I picked up the car to today.

Supposedly the car knows it was filled because the door opened, the gauge went to the max, and the range went to a new max from my "tank average MPG" * 10.6 gal.

It started at 511 miles when I picked up the car which would be 48 MPG from Toyota testing.

It currently shows 474 miles for a full tank - which says the car thinks my Tank Average is 44.7 MPG, but it is displaying 99.9 MPG in the MID. WHY?

No - totally redesigned user interface and data availability.

 

I know the MPG of the car six ways to Sunday. This thread is about the Prius Prime "Tank Average" information display being 99.9 when the car thinks the Tank Average is 44.7 MPG.

 

The refill at the start of the test was 4.354 gallons, the fuel guage went up to max and the estimated gas only range went down from the original 511 miles to 467 miles meaning the car thought the "Tank Average MPG" was 44.0 MPG.

After my HV test, the car "thinks" the Tank Average MPG is now 44.7 MPG but it still displays 99.9 MPG in the Tank Average MPG Multi-Information Display.

This thread is not about how to measure MPG, it is Why is the displayed value 99.9 when the car "thinks" it is 44.7 MPG (a very believable and useful number). I cannot use the MID Tank Average value, but I believe I can trust the range next to that little fuel pump icon.

I tend to want to know raw data like my average MPG for a particular type of drive and how much gas is in the tank, then make my own range estimates. It is looking like that gas range estimate might be believable. Prior 2009 Prius fuel gauge had 10 pips, that I never planned for going below two pips remaining. This tank display doesn't have countable pips.

 

I reset Total Average in HV mode to zero when I filled up and have not yet burned any dinosaurs, or where ever oil really comes from.

I have the feeling "Tank Average MPG" is only valid for a non-prime.

 

Works wonderfully for non-prime, totally bogus for prime.

Using the same software for both without tailoring is just lazy, but hey we're talking about an inexpensive car aren't we? oh yeah not.

 

Toyota is counting on most folks to be thinking along those lines.

I'm an obsessive "techie", and don't mind when a product doesn't offer information or a feature, but it bugs me really, really intensely to be lied to by software. I spent 45 years writing software. I was passionate about every feature being bug-free and useful. When the Prime tells me I got 57 MPG but the real number is 42, I really don't care that 42 is still a darn good figure compared with my wife's premium gas hog at 20, my car lied to me and not by a little round off error or limiited by variability. It inflated the "goodness" by 36%. That is just flat lying to me. I'd rather not have a gasoline MPG feature.

Luckily I won't be using HV mode much, so it won't annoy me that often.