Two weeks ago I got 24.9 mpg from PGH to Emerald Isle, NC with a "full load" and a Sears X-20 Cargo container on the roof. This was in a 2014 with Sh-AWD (Tech). Quite a bit better than the 16-18 mpg on similar trips with our '06 MDX and same car top carrier.
Back in June, we got a little over 27 mpg from PGH area to Bilger's rocks in Clearfield Co, PA (lots of hills, etc.) and I was very happy with that on that drive. Avg. speed was probably 50 mpg though. This was all trip computer and no hand calcs.