Okay, so I just got back from our trip out to the midwest and back.
Starting Odometer: 465 miles
Ending Odometer: 3771 miles
Tire Pressure: 44psi all around on Hankooks
Miles Gallons MPG MFI Speeds Notes
Tank 1: 516.4 11.918 43.3 46.9 55-60 pulling 500lb trailer
Tank 2: 670.2 15.523 43.2 46.6 55-60 pulling 500lb trailer B5
Tank 3: 799.3 16.207 49.3 49.8 60-65 55 miles to zero
Tank 4: 853.7 16.987 50.3 53.8 70-75 35 miles to zero
I think the MFI was actually fairly accurate the last tank, I'm just not that accurate at getting the same amount of fuel in the tank every time. I'm still not getting more than 17 gallons in the tank, but I'm not willing to go down to zero, 800+ miles on a tank is plenty.
Nice! Loving the looks of tanks 3 and 4.... pretty normal for trailering, messes up the clean aerodynamic Cd of the car. You are well on your way to a 52 to 54 MPG tank one of these times... 500 miles per tank if you felt you did a good job knocking down the MPG's on a tank.