I know this has been brought up in other threads but I haven't seen it in this one yet...

Bear in mind many back-to-bank tanks will show individual skews due to overfill/underfill. For example, if you check my last 2 tanks, they were hand-calced at 58.1 and 49.8 MPG. It wasn't intentional, I just always cut off at first click. Pretty big difference, but the display read 56.3 and 53.3 for them, which was a whole lot closer. If you took the average of the displays, it comes out right about to the average of the manuals, only generally speaking, hand-calcing is a more accurate method. Since your second-to-last tank was such a stud, maybe it left you filling a bit more on this one when you took it in, even if the comp hadn't detected the lighter fuel load that whole trip.