I have often thought of EGR this way....

Next time you have a really good bowel dump, then grab a handful and eat it. Then your next dump should be cleaner than the first, right?

All the EGR does is reduce various oxides of nitrogen by keeping the burn temperature lower and displacing fresh air. To go about reducing just one "questionable" green house gas, they stop up the engine quicker and requires more fuel to gain the same level of performance which increases carbon output. Wonderful thought process behind this.

That being said, the most effecient and cleanest engine would be a pre-egr engine with the new DEF system. It would operate at peak fuel effeciency and the DEF could take care of the NOx generated by hotter burns. Would hardly need any DPF to clean up soot, since this setup would produce minimal soot because of the effecient burn. I really have no real issue with DEF and DPF being used on new engines, but darn it, get rid of that EGR.

 

I remember the old days of pulling a grade and flame running out the stack. Now if thats not a way to burn particulates, I don't know what is. I have a '10 Freightliner with a 60 series Detroit. I've found if I let the truck pull harder on the hills, I hardly ever get a DPF light. I generally don't run too hard on the flat, about 60-65. (I'm getting to that age where running too fast stresses me out) All that being said, I'm gettin 6.7-7.2 MPG.