The old “chicken/egg” question. Do the penalities of increased fuel consumption and maintenance costs offset the better efficiency of “dirtier” engines ? IOW is a little bit of something noxious more injurious than a lot more of something marginally less so ? >PS
As you might expect, most of this is centered around California and some of the large metroplex cities back east.
We’re all paying a very high price for their cleaner air.