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Old 08-26-2009, 10:16 AM   #1 (permalink)
Engineering first
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Join Date: Mar 2009
Location: Huntsville, AL
Posts: 792

14 i3-REx - '14 BMW i3-REx
Last 3: 45.67 mpg (US)

17 Prime Plus - '17 Toyota Prius Prime Plus
90 day: 58.25 mpg (US)
Thanks: 80
Thanked 196 Times in 126 Posts
Calibration of 2010 Prius MPG indicator

With 109 samples, manually collected from the PriusChat community, we now have enough data:

The blue 'dashed' line is the desired, calibrated values. If the indicated mileage were accurate, the data points would bound either side of the dashed blue line. As for the upper, outliers, they are still sparse but they seem to be around the trendline. This is not enough to 'bet the farm' but enough to not worry too much if extended.

The other interesting aspect is the double-humped, MPG distribution:

This closely agrees with the double-humped distribution from the small number of user mileage reports from the EPA database:

At this point, the ball is in Toyota's court. Absent some way to modify the software that calculates the indicated MPG, we just need to understand the problem and depending upon the requirements, there are these options:
  • use pump MPG for accuracy and indicated for relative MPG performance
  • use correction formula: actual = (.85 * indicated) + 5.3
  • use 3d party MPG indicator: scangauge, supermid or others (mpguino)

Feel free to share this with other Prius groups and thank the PriusChat community for their data contributions.

Bob Wilson

2019 Std. Range Plus Model 3 - 134 MPG3 || 2014 BMW i3-REx - 117 MPGe, 39 MPG
JuiceBox 40 Pro (240 VAC, 40 A), KHONS portable (120-240 VAC, 12-32 A)
Retired engineer, Huntsville, AL (five times AutoPilot saved.)

Last edited by bwilson4web; 08-26-2009 at 10:40 AM.. Reason: Correcting alternate MPG device lists.
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