According to this web site: http://www2.mazda.com/en/publicity/release/2016/201612/161215a.html
The Japanese version of the 2017 2.2td gets 23% better mileage than the 2.5 gas engine.
Well then for me, that would be 37 MPG. For someone like Kaps who drives at more reasonable freeway speeds, that should put it at 40+ easily.