Seafoam (unless they have a new product) is most effective when fed through the intake, allegedly cleans out the combustion chambers, intake. I haven't used it on an MB, but it did help clean out the intake and plenum on my mitsubishi when I used it, but no real performance difference along with a ton of smoke when using it. I would guess that adding it to the gas would be advertised to clean injectors...but there is a lot of snake oil out there...

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth