Freightliner has been running the Mercedes diesels in the Business Class models for quite some time now. It is nothing new, in fact the Business Class Freightliners have been around since 95. The engine options available for the business class trucks are CAT C7 and C9. MB900 and MB4000. And starting about mid 2005, Cummins is back again with an option of the ISB or ISC common rail.