not all 0w40 mobil 1s are created equal.. same goes for other brand synthetics.

the front of the correct mobil bottle says european car formula. the back label say meets mb spec 229.5 ANY brand syth. that meets mb 229.5 is ok. kendall comes to mind-but not ALL kendall. you have to check the labels.

what goes wrong if you don't? don't know, don't care. the right stuff is the right stuff. otherwise, mb would go the cheaper route and say pour anything.

as far as time and mileage, mb in 2009 say 12mos/10k miles, whichever is 1st. 40k on the trans and filter. good luck, chuck.