[mwebb]

Originally Posted by ConnClark

To the contrary, what auto makers must do to meet EPA mandates for emissions is very detrimental to fuel economy. To claim otherwise is a very poor argument.

"the new diesel common rail systems use intake restriction to improve EGR flow at cruise , so partially restricted air filters will have little to no detrimental effect on FE ."

whatever the above reply is meant to say ...
on a common rail diesel system at cruise , a restricted air filter still will have very little to no detrimental effect on FE

and
generally speaking
clean emissions do not have a detrimental effect on fuel economy as overall efficiency improves as overall emissions go down .

consider a carburated system from the 70s and a 2012 any car from now ....
same mass ,
FE is better by a huge percentage and emissions are greatly reduced on the
current systems compared to the 70s cars

except for
particulate filter regeneration on the new common rail diesel systems , on the cars i work with , FE was better on the older systems that did not use
particulate filter regeneration and did have engine management systems

those are the facts