Answer
Make sure to keep all records, of oil changes especially. mobil one is by far your best bet. if you can find it, use 0w40 esp formula, its a grey bottle with green on the label. depending on the mileage you should keep a close eye on the oil level. if your ml is consuming oil it could fall under a court case and qualify to be fixed at no cost to you. you would have to pay for an oil consumption test but it would be reimbursed if it qualified. this is only available at mb dealers.