Is the 6.4 Direct Injected? Because my 3.5LEcoB DI meter is right on. And I've wondered whether it has anything to do with the Direct Injection allowing the engine to know exactly how much fuel it is using.
Have been hand calulating from the beginning and the difference between the gauge and hand is only 0.07%, and I'm sure that most of the error is in topping up the tank.
What's nice about having such a precise guage (two of them in the F150) is that you can then use it to separate towing from non-towing mileage.