| We discussed the trip computer accuracy on Ken's M-Class list a while back and folks compared it with what was put into the tank. As I remember most folks got pretty reasonable results. The data input comes via the CAN-Bus from the 4ETS controller (wheel speed signal), engine controller and instrument cluster (fuel consumption). The cluster reads the fuel level. If there's a problem with the fuel level sensor in the tank it could lead to erroneous consumption figures. With sulfur in the fuel a tank after being filled up shows low or empty. Driving with that setup would presumably show fuel consumption figures which are too favorable.
The service manual only says it uses "average" fuel consumption, but not what kind of average. I checked on the webpage of the trip computer manufacturer, since taken down, and it explained the algorithm as "moving average". Maybe this was in regards to the 2002+ versions, not sure. When I measure it for comparision it's usually under 62 mi, so it would be the same figure for either method.
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