I guess I shouldn't (and don't) complain about fuel mileage considering I have a ACERT C15 in my 48000 lb truck conversion with a 2010 Silverado in tow.
Keep in mind the C15 is 20% larger displacement than the C13 (928 ci to 762 ci)
I drive this at posted speed and at 75 mph it is taching 1500 rpm which is 150 above the sweet spot. Yeah 1350 gets me .4 mpg increase but then I become one of those rv's holding up traffic-no thanks.
I love people talking mileage and comparing this to that. As someone recently posted, remember conditions, weight, weather, traffic, summer/winter fuel, everything effects mileage.
If mileage is the end all to be all-lets get the VW diesel and sleep under the stars-PASS.