I took a trip yesterday about 130 miles one way. I went the speed limit 75 and some in town driving (15 miles tops) and got 15.3 mpg. I followed some slower trucks home and stayed between 68-70 mph all highway and got 19.3 mpg. I got just over 18 when I brought it home a couple weeks ago. The only thing I have done to it was put an ARE cold air intake on. This is a 2002 F250 4x4 EC SB 7.3 296500 miles. I was told it was all stock but the transmission has been worked on. I went to service it and after spinning the torque converter several times, found there was no drain plug. It sucks for me because I wanted the serviceability of the '02 model. This is my first diesel so I am learning slowly.
I was wondering if this converter has something to do with the mileage I have been getting? What converter would be used to replace the stock converter?