When I first got the Deville and drove it home from Winston-Salem, NC, I was amazed at how the initial MPT and distance until empty recalculated, especially on the highway. When I hit highway speeds and maintained a steady 65 mph for a while, the calculation of the distance to empty slowly crept up at highway speeds at z steady throttle point. I think it finally settled on about 520 miles on a full tank. And it was close.

I haven't seen anything like that since, but I haven't been on any longer highway drives since then. But today, on the highway for about 5 miles, I get off the exit and decelerating gently at about 42 mph, and it shows 70 MPG! Then, later on, a steady 40 mph becomes a more reasonable 36 mpg. Just 2 mph less than what was giving me 70 mpg.

Never seen a 70 mpg before ;^) Normal computer math based on speed/incline/throttle, or does something need to be reset/relearned? This car cracks me up sometimes.

Yes, should have had headlights on, not juts Twilight ;^)

The calculation has more to do with commanded torque than vehicle speed. If you could keep going down that off ramp with your foot far from the pedal at 42MPH, you'd probably actually get 70MPG and be able to go 1,400 miles on a tank. I haven't found an offramp like that yet. If you were giving it a little tiny bit of throttle at the same 42MPH, that number would be a bunch lower.

Those numbers are funny. The immediacy of the computation is commendable, and unheard of a couple of decades earlier. It also leads to irrational numbers like that.

DTE is more rational. It does a calculation for how full the fuel is and what kind of fuel economy it has gotten until now. They leave a little bit of margin on the end of that just in case your economical highway drive ends with a frantic race through the streets of Redondo Beach to the Portofino Inn.