Attention: TDR Forum Junkies 
I just made two 420 mile drives going and coming on the same route. About 30 miles were thru the Blue mountains of NE Oregon. On the first 420 miles going west I set the cruise at 65 and stayed there 99 % of the time. Hand figured was 21. 21 MPG.
The return trip was with a big tail wind in the Columbia River Gorge going east and that was with the cruise set at 70. Hand figured at 21. 03 MPG.
The fuel tank was filled right to the lip both times which took some time at the pump.
On these trips the overhead reading was about 2. 5 MPG better than the hand calculated which is about right from what I have read.
I run 8 oz of Diesel Power Service and 4 oz of MMO.
The last 10,000 miles the milage has improved and the Edge Chip and the BMRP exhaust has helped over the last 2 to 3 thousand miles.
I feel this is very good for the automatic transmission.
