Just returned from a 7,360 mile, 22 state, 2 month trip in our 2012 24' Nexus C, E-350 with the V-10, no toad. The trip took us from Tucson to Maine and home again. Our best mileage was 10.75 and the worst 8.2. We averaged 9.35 which included a lot of city traffic, grocery getting, dirt roads etc. About 40% of the trip was interstates at 60-62 which usually got us 9-10. Lots of back country two lane blacktop at 50-60 pushed us up to 10+but driving into 25 to 35 mph winds on three consecutive days generated the 8.2.
Weather and road conditions along with your resulting speed have a huge impact on your real world mileage. I run with the Scan Gauge displaying both average and real time mpg along with trans fluid and coolant temps. Every fill up confirmed what the Scan Gauge had been reporting.
:C