They could still be meeting the EPA standards without DEF today. If they were willing to live with those issues.
This is not true. They couldn't even meet EPA a few years back. To even get their heavy EGR engines on the road they had to use credits. When those credits ran out EPA said meet the new standard or quit selling dirty engines; your choice. :E They decided to meet the new standard and all was well with the world again. :)
Well........that was until Ram marketing had to back track on all the shirt talking they did about DEF. :B