As I enter my 3rd year of TCH ownership, my curiousities have turned to the "Cruising Range" (CR) calc on the MFD. There has been some discussion in the past on exactly how this is calculated. I've spent the last couple of weeks paying a lot of attention to it while trying not to crash into anything and have made some observations:

• One thing I wanted to test was if instantaneous fuel usage had any impact. I have a few forgiving roads around here where I can maintain EV over about 3+ km. I wanted to see if the CR display would continue to click down even if the engine was not running. Yes, even without the engine running the CR display still counted down.
• Another thing was how much the fuel guage/sensor readings play in the calc. We know the CR resets when you fill up. Some have suggested it might be triggered by the fuel door opening and closing, but from past experience from partial fills I'd have to say it is the fuel guage/sensor that is used to calc and reset if need be the CR.
• How does the calc respond to variations in fuel levels (ie sloshing about, starting up after an ambient temp change may have affected the volume of fuel, normal fuel usage, etc). What I discovered was that the CR display will drop by 1km exactly every 0.5, 1.0, or 2.0 km. It seems that if the calc determines your current CR is too high, it will drop the value by 1km for every 0.5km of driving. If you're in good order, 1 for 1, and if the current CR is too low, it will drop the CR by only 1km for every 2km driven. I'd be curious to know how this translates to a US car in miles. Its been suggested that US cars run in metric and do conversions for (or in) the instrument panel for operator display. I also noted with this that current trip FE (the 3 level bar graph on the MFD) didn't seem to factor much or at all. I had times where I had full 3 bars and the CR display was dropping every 0.5km and times where the trip graph had no bars and I was getting 2km for every 1km on the CR.
• Finally, obviously the calc involves some reference to your average FE. I set the trip meter "A" to 0 at fill up and then proceeded to watch the sum of the trip meter and the CR to see how it changed over time. At any given time, you would figure that the sum of how far you've gone + how far you can go should pretty much be your CR with a full tank. I noted at the beginning that it started out around 870km and thru the tank of gas it drifted around a bit as the adjustments were made to end at about 855km. However, after filling up the tank the CR then displayed 895km. Seems that at the point of fill up it become 40km more optimistic. I'm wondering if this reset of the CR (and Tank Ave) display triggered the storage of the current "Tank Ave" and dropping an old one out in some kind of queue. If so, it probably dropped out an older Tank Ave from earlier in the year when it was colder and my FE is poorer. I will probably have to track several Tank Ave and CR displays at fill time to see if I can confirm this and determine how many Tank Aves are used.

Seemed like a good useless Friday afternoon topic