See also:

Belt height adjustment
You can adjust the seat belt height on the driver's seat and the front-passenger seat. Adjust the height so that the upper part of the seat belt is routed across the center of your shoulder. ...

Mercedes-Benz M-Class Owners Manual
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Downhill gradients
On long and steep gradients, you must reduce the load on the brakes by shifting early to a lower gear. This allows you to take advantage of the engine braking effect and helps avoid overhea ...