I recall when egr first came to light chevron put out a video about CH-4 specs how it changed i recall them showing the pass/fail standards somewhere in order of 3% then going up to 10% suspended soot as test to see if it kept the soot in the oil and not fall out and clump clogging everything. 3% seems pretty low..

http://www.highwaystarmagazine.com/yourjobfeature.cfm?ID=187

__________________
2004 Infiniti G35 3.5L 6mt Coupe 73K miles 25.6mpg ytd
2001 Green Audi TT 225 AWD Roadster 71K 6sp 30.9mpg >>STOLEN<<
1982 300D Turbo 231K 120hp? 28.1mpg YTD

While the oil may suspend more than 3%, the hydraulic lifters used in Mercedes OM60x engines don't work well with that much soot suspended in the oil. I only get approx 1% in 10,000 miles in my OM603, so it's not an issue for me anyway.