Wow, just found out why the 2016 26XD is performing soooo much better than the 2015 23XM... It's a six speed.
Gosh, It's quieter, smoother, does much better on hills (we can leave the cruise control on without screaming high RPMs). It just cruises up hill at about 2900 RPM, and best of all, we're getting a bit over 11 MPG!
I had no idea that it was a six speed tranny when we bought it, so it's a very happy surprise!