Took the trailer to town yesterday to pick up my tractor after having some work done on it. Got some interesting MPG figures on this rig in the process. On the way to town traveling empty with the trailer I seen 22 MPG at 55 MPH. At 40 MPH I seen 30 MPG. These numbers really show the power of aerodynamics. At 40 MPH drag is much less a proportion of the forces loading the engine and I was only paying a 2 MPG penalty. At 55 MPH I was paying a 5 MPG penalty.
On the way home it was a entirely different matter. I was looking at 18 MPG at 40 MPH and only 14.5 MPG at 55 MPH. I find this interesting because in some respects it models towing the Apex trailer. The weight is within a couple hundred lbs of what I would be if I were towing Apex, but without the frontal area. The air does not like the irregular shapes of the tractor sticking up, including the roll bar and roof, however it does not have the frontal area of 62 sq ft that Apex has. This results tell me that 14.5 MPG is certainly possible towing Apex possibly 15 MPG is a reasonable expectation.
Next week we are removing the Aerolid for open bed test of towing Apex in order to acquire a baseline MPG figure for the truck and trailer. I hope to acquire a baseline with a bed cover also. I am interested in 55, 60, and 65 MPH specifically.