[Diesel_Dave]

Okay, so here's an update.

I'm now convinced that the fuel pump was correct, that is I DID put 37.5 gal in the last fill up. One factor that convinces me of this is that I went 300 mi before getting to the "F" mark. Also, I just filled up again this morning. I went 1,243.3 miles on this last tank! Filling up this time (again until I could see the fuel level in the neck), I put in 34.2 gal. That's pretty much what I would normally expect. My "low fuel" warning had just come on the overhead about 15 mi earlier. In the past I know I've gone about 30 mi after that and filled up with about 34.7 gal.

So, the pump was correct, but somehow I put an extra ~3 gal in last time. That means my 3-tank, 90-day, & lifetime FE are all correct now--it's just that the calculated FE for these last two tanks are skewed in favor of the latest tank. Nominally they're 28.6 mpg & 36.3 mpg, respectively. They should be about 30.8 mpg & 33.1 mpg. Those numbers make a lot more sense with the trends I've seen from my in-cab display.