ok, i don't need to hear about duramax or cummins, this is what i got. I bought this truck new in nov. 02, the last of the 7.3s, 6.0s were on the lot. started out new with 18 and up mpg. ever since it has steadily fallen off to the point of 2 weeks ago, I went on a trip to get a new used WB, i left home with a full tank, figured i could make it there & back no problem, wrong! pulling my 16' trailer I got 9.7 mpg, half the trip the trailer was empty and on the return it only had 1 36"wb on it. This is the worst milage i have ever gotten other than plowing in big storms. It has been suggested to me that maybe my torque converter is not locking. if this is the case I sure dont feel a difference when driving. any Ideas, and please don't tell me to get rid of it. at this time it is not in the plan so that is not possible. oh ya, and during daily use with no load or trailer its still only about 14 +or-a little. Is this normal or is something wrong, dealer said its normal.