All vehicles with diesel engines sold in USA are REQUIRED to be fitted with a diesel particulate filter beginning model year 2007. ULSD is the concurrent requirement to provide protection to these filters. My GL320CDI produces no smoke and at 21K miles there is zero soot on the chrome exhaust extensions.

Black smoke is of course visible particulates, and there shouldn't be any emanating from MY 2007 and newer diesels, even the big trucks.

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles