When dealing with these such issues, it will say on the customers copy of the repair order: "recommend using 89 octane gasoline". This is the info that MB has given us. This topic seems to get people as fired up as a K&N filter thread. If you want to spend more money to have your car not run as well, by all means do it. The gas pumps at my dealership have had 89 octane in them since the afforementioned 104 issues.