Sfaulken, I think we're making the same point. My mind was going to the smog pumps and air injectors of the 70's, but I'll agree that things didn't really get dialed until the 90's like you said. My point is that gasoline emissions equipment is pretty dialed in. Modern diesel emissions seems to be leaps and bounds better than it was 15 years ago too. My experience comes from the 2005 f250 6.0 that I loved/hated, and the 2010 bmw x5 diesel that I still own. The emissions equipment is problematic in both of those vehicles, but you hear a lot fewer problems with def, dfp's and egr's than you used to. Yes they're still expensive to replace, but that's not the point of this discussion.