Hello dear R community, the change of the air filter is mandatory only every 80.000km, but without any problems to do it yourself. First the engine must be ‘unloaded’, to remove two hex screws SW13 on the right and left, pull off the front rubber seal and remove the rubber buffer from the middle of the windscreen wipers to the water flow. Then the upper cross-carrier can be simply pulled forward over the engine (picture 1). Then I try not without me to bed again the SLK R171 homepage of Mr. Günther Lang. There the change of the air filter with the M272 is described very well.