First of all, I've been running biodiesel in various blends since 2001. My E300 loves B20 with zero modifications or maintenance changes required. I have run a few tanks of b100 in it, and it sounds electric. However, IDI engines are better designed to handle biodiesel. I've seen some NASTY pictures of biodiesel(FAME) and WVO/SVO use in HPCR injection systems (like your CDI). There is a phenomenon called 'flocking' that has been known to occur in high pressure b100 situations, due to bio's wide variance in viscosity compared to regular diesel fuel. I did run b100 for 35k miles exclusively in my 2002 TDI without problems, but there is a significant power and mpg loss at that concentration. My advice is to feel good about doing your part for society and the environment, and your car, by running b20.
Aus makes a good point noting the differences. I know volkswagen in Europe and other countries approves RME - bio made from rapeseed oil (a relative of canola), and I'm not sure which MB approves.
FWIW - at least with the crappy diesel fuel quality here in the states, folks should be changing their fuel filters every 20k or less anyway IMO, considering they are about $8 or $10 max and comparing that to the price of injectors
