Overfilling theory (input needed)

[Charon]

I see the discussion seems to have shifted from getting the most accurate mpg figure for a given fill to getting the longest range on a fill. For range, the semi I used to drive averaged about 6 mpg but had a range exceeding 1100 miles at mostly highway speeds. I never ran it dry and usually filled it about once per day at somewhere around 500 miles. Its secret to long range was simple - two saddle tanks holding over 100 gallons each.