The newer models don't smoke at all. My 2008 ML's computer will not let it smoke no matter how hard you floor it. The common rail system will not let it inject more fuel than it can burn. The particulate filters take care of the rest.

Indirect (mechanical) injected engines do not have as tight a control on the fuel quantity, so they will smoke under heavy load.

Just remember with the current political climate that heavy smoke is now a bad thing. Unfortunately VW really killed the perception of diesel in the US, even though they got caught not for particulates (the black smoke) but oxides of nitrogen (invisible but supposedly very bad). But most people equate black smoke to killing the planet.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech