Well, the instant fuel consumption reading while idling is never accurate because when you are not moving, you are infinitely consuming fuel. The instant fuel consumption simply shows 30l/100km as a base reading when you are stopped.

To view instant consumption, you may dive into the hidden on-board computer functions. Start with the vehicle off, key out.

1. With your left hand, hold the S/R button in the instrument panel, while turning the key to position 1. The OBC will read "test __"

2. At this point, keep pushing the S/R button until you reach "19._". Then, it will alternate between on and off. When it shows off, push the S/R button until it shows "4._"

3. After a second or so, it should show "4.0 _ _ _ _ _ ". You may start the vehicle at this point. Numbers should show up in the blanks as you accelerate. This is instant fuel consumption. "136" translates to 13.6 l/100km. Note that with a cold engine, fuel consumption is substantially higher.

4. Under light acceleration, fuel consumption should spike at the beginning, around 50-80 l/100km, and it should steadily decrease. At highway speeds on a flat gradient, it should be between 6-11 l/100km cruising at 100km/h.

5. When you coast and let off the throttle at anything above 50km/h, the consumption should drop to 0 (and the thing should read "000"). This applies to manual transmission vehicles and '07+ X3s with the newer automatic transmission with earlier torque converter lock up.

Here's mine under light acceleration (I apologise in advance for the less-than-stellar quality):