I know I may be in the minority, but I WANT the cleanest air we can have. If it means I will pay a little more and get a little less fuel mileage, I don't mind.
For those that have never seen how bad SMOG can be, like in the 70's before catalytic converters, it is amazing. And, the newer engines over the years have given us a lot more HP with smaller engines and better economy.
I absolutely have no smoke coming out the tailpipe of our Dynasty even on hard pulls. Burns clean and no trouble with the particulate filter system in 68,500 miles.
The new coach will have DEF and I expect about 6.0-6.5 mpg's because of the weight (54,000 lbs).
Safe travls,
MM.