Kreen is great stuff. I had an E300 with almost 300k miles some blow-by and injector knock in the morning. Used a quart 500 miles before oil change. Talk about change it cleaned out 300k worth of sooth sitting in the oil pan, loosened up stuck rings and some was added to fuel as well and the injector knock was gone.
Now to avoid Hazard overcharge order only in quart cans. You also get a Free can of Kroil. By the way even though their web site says no California orders they do ship them as I know some members in MB forum who recvd their orders. Best additive in the market.