You have to initiate the level measuring after going through a couple steps on iDrive. The next to the last step or screen says the car must be in park, on a level surface, engine warmed up, etc (I can't remember if it says the idle will increase slightly, stay off the gas). You then select "measure" through the iDrive, the idle increases to around 1100 rpm, and the next screen is a horizontal bar that starts to gradually increase with an increasing percent figure as the measurement is taken. It takes about a minute or two (seems longer) for the measurement to complete. Then the final screen shows the familiar vertical bar, like a dipstick, with the oil level.
You definitely can't measure the oil level while the car s in motion.