Bio does a pretty good job of cleaning the gunk out of fuel storage systems. I usually carry an extra fuel filter (both for the benz) in the vehicles during the summer (at home we run BD in the summer, mostly B20 - its cheap & I use a lot). I've been glad I did on a few occasions. The benz filters are cheap, & easy to change. BTW the OM617 is pretty forgiving - it will handle B20 just fine. One of my friends has over 200k of B20 use on his 85 300SD (total miles are over 500k). It works just fine.