New Bosch diesel technology provides solution to NOx problem

for ideal thermal efficiency you want exhaust gases as low as possible, ideally ambient temperature, so, raising exhaust gas temperatures will have a hit on thermal efficiency (mpg) at low load. reducing egr will improve thermal efficiency. reducing soot load will mean less fuel burned to clean the DPF. Not sure the overall impact on thermal efficiency (mpg), but meeting NOx emissions is a requirement, so you take what you can get.