Our Compass calculated and computer onboard display are generally within .2-.3 mpg of each other which I see as a very reasonable level of variation. We use Roadtrip which allows me to keep track of a variety of pieces of info relative to our cars.
We drive our 6 speed manual transmission conservatively and are seeing an average of 25.4 mpg in mixed city driving, most trips under 6 miles. So far we are pretty happy with the mileage.
This week we are taking our first real trip with the car so we should see how it does over extended highway miles. We will have a hitch mounted cargo bag so its unlikely to be the best it could be but comfort inside outwieghs hypermiling when in the car for 14 hours.
Just ordered a Compass Lattitude, Blue Pearl Metallic, 6sp manual, towing, convenience, safety, lighting, cold weather due early April 2018