Good suggestion from that mechanic. I always drive in slow traffic in "3" in the '87 300D. Keeps the brakes from wearing and warms up the engine better if its cold. Engine dynamic braking. I can't seem to teach my wife to do that however
the 240D is a different set of conditions however

__________________
'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!