content: The urea retrofit isn't that expensive, for starters...  It's an entire electronic fluid injection system, coupled with a dedicated catalytic converter, it's not at all cheap. In fact, the manufacturers who've chosen not to adopt urea injection have done so because it's a very expensive system. Edit: What's with diesel fanboys and the downvoats? Can you prove me wrong here? Go back to Reddit if you're going to throw a fit about facts you don't like!