Which mode do you use?

[AzNMpower32]

Originally Posted by rh71

I have been looking at it more carefully lately. Anytime you're accelerating from stop, even lightly, while in 1st & 2nd gear, it WILL be low MPG (indicates 12/13 at most). Once you reach 3rd/4th gear, and despite being a bit heavy on the pedal to keep acceleration at this point, your MPG will improve a lot.

The weight of the vehicle has a lot to do with the figures and of course stop-and-go (city) which we already knew about. My point is, what's interesting to me is that MPG does not always correlate with how heavy you are on the pedal, according to this gauge. Also to my surprise, DS mode shows the same situational results on the gauge. Seem right to everyone else?

It's a lot to do with physics (none of which I have learned thru school). The heaviest fuel consumption will be accelerating from a dead stop, which is magnified by the mass of the X5. It's normal to get consumption values like 50-75 l/100km for the first few seconds when accelerating. Once you're up to about 60km/h, you should be able to make use of the gauge, and it's very good for minimising consumption on the freeway.

With the new torque converter technology, it's not a surprise that the gauge behaves similarly. The newer transmissions lock up the torque converter after takeoff even in D, and only decouple it below 40km/h. Thus with the converter locked and no throttle, fuel consumption drops to 0. The higher overall consumption SD comes from the higher revs the transmission runs up to before upshifting, and the more frequent downshifts, which also increase fuel consumption since the lower gears are not as efficient as higher gears.

If you have an older X5 or X3 with the 5-speed auto, SD and D makes more of a difference, mainly because the torque converter does not lock up until ~80km/h in 5th gear. When the converter is not locked, there is a minimal amount of fuel consumed, usually 3-4 l/100km. But even those with the new X5 can see: as you coast towards a stop from say, 70 km/h, you'll see that the needle shows 0 consumption until ~40 km/h, at which point the needle rises a bit, reflecting the decoupling point.

I haven't taken a single physics or engineering class in my life ever, but this is all stuff I've learned thru careful observation. Sorry for the metric, but as you can see the fuel conservation gauge really makes more sense this way (because the car was designed in Germany, duh!) 20 l/100km = 12 mpg.