The best possible mileage/power with a diesel comes when the engine is operated at its torque peak. Operation at rpms significantly above this peak will result in low mpg. Judging by the way MB geared their US diesels they peak at 2800-3000rpm. Lowering the cruise rpm too far on an MB likely will lug the motor too much. The MBs I have driven only get up on the boost at about 2300-2400rpm at the earliest. A GM diesel is not a good comparison as they start making boost at 1600rpm with a torque peak at 1900rpm, redline at 3600rpm. I know, my truck turns 2100rpm at 72 mph and gets 21mpg on the highway. The best MB mod it would be to use a rear diff from an 85 or a wagon with the 2.88's (i think) as opposed to 3.07's. This should drop your cruise to 3000rpm at 75mph. Not low enough to lug the motor and still allow you to keep up with traffic. RT

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