Same Penske who run NASCAR and Indy teams? What about Caterpillar? Many trucks had them as engine option.Daimler(Freightliner/Western Star/Setra Bus) pushes Detroit Diesel(they bought them out from Penske during the 1990s), PACCAR pushes their own engines, and Navistar is now pushing their MAN rebrand. The new Detroit Diesel engines are rebranded Mercedes engines. Cummins is a option for all of them.
However, Daimler wants to split into two - Mercedes cars as one, Freightliner/Detroit and Mercedes truck/bus into another company.