The DPF was mandated by the 2007 EPA requirement. Any engine built after 1/12007 has the DPF. most coach builders managed to stockpile enough engines to hold off the requirement until the next model year. 2010 was the same story for DEF. Engines built after 1/1/2010 had to meet the requirement. There were some exceptions due to engine builders using credits issued by EPA or by paying a fine per engine sold. Again, coach builders bought up enough inventory of engines or chassis to get through the 2010 model year before using DEF.
