The MBZ FSM for the OM617.95x states that offset keys are available to correct performance complaints. There's absolutely nothing in the documentation that specifies the keys are only for use on good chains.

From the FSM:
"If the (cam) timing requires correction, install an offset Woodruff key or, if the chain is excessively elongated, install a new timing chain."

In addition, the FSM publishes specifications for the amount of acceptable chain elongation in units clocking more than 20,000kM (see graphic). To me, this, along with the fact that MBZ provides four different key offsets, implies that these keys are available for use in economically correcting the routine wear (elongation) of the timing chain as opposed to outright replacement of the component.

There is no stated 'maximum' mileage for the chain nor is there any specification for change intervals as there is for vehicles equipped with Gilmer timing belt cam drives. Once a maximum offset correction of 10° is reached on the OM617, apparently, the chain is 'excessively elongated' and should be replaced.

I have a hard time believing that Mercedes would knowingly and willingly mass produce engines which, with 0kM on them, might possibly have as much as 10° of cam timing variance, expecting their servicing dealers to correct this problem after a performance complaint was received from the customer.

The more plausible (and Teutonic) explanation is that MBZ engineers had arrived at an economical method of accomodating the 'x' factor of new cam chain elongation which is experienced in the first 20,000kM of operation.

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