2001 F250 PSD 4x4, XLT Ext cab, 49K miles thus far, tow about 9000 pounds long distances. 3.73 rear. Check milage on every tank.
Non tow, 16.25 to 17.8, all time high was 19ish, several times.
Tow, 13.6 to 14.5
boat and truck combined on the scales is over 15K pounds.