Well i just got back home after a three day 2000mile trip. Basically Houston to Atlanta but a little more. From Houston to Atalanta was ran with a empty 35ft Dove Tail, Truck + 8000lbs for the trailer. Here is the MPG Number Report for that
1st Fill up, 16.9 gals, $70 ,$4.13gal, Average 12.6 MPG(This was with the trailer running around but had not left for the trip yet)
2nd Tank(In to the trip now)
$131, 30gals, 327miles, 10.9 MPG, $4.39
3rd Tank
$133, 31gals, 334miles, 10.7 MPG, $4.25
4th Tank, Loaded Leaving Atlanta GA. Total Weight of Truck, Trailer, and Load, 25,534lbs (1/2 tank of fuel) According to CAT Scales.
$129, 29.5gals, 306.8miles, 10.4 MPG, $4.37
5th Tank
$123, 27.5gals, 256 miles, 9.3 MPG, $4.46
6th Tank
$142, 31gals, 269 miles, 8.67 MPG, $4.55
7th Tank
$144, 32.8 gals, 272 miles, 8.3 MPG, $4.39
So Over all MPG was 10.7, Money Spent, $871, Total Miles which are not all listed was 2000(give or take 50)
Running Up to Atlanta the truck pulled the trailer pretty well. I kept the MP8 up and the PMT on Tow. I never just got on it I just used the power for 6th gear.
Now with the trailer loaded was a different story. I kept the MP8 off and the PMT on Tow for all of this. I found out real quick that the 68RFE hates Slow traffic, Stop and Go Traffic for that matter. It did not take long for the Trans Temp to HIT 220 Degrees. The Coolant stayed between 205 and 215 which i am happy with that. The Tranny.
Going through the hills(Over Passes also or anything with a incline) I was forced into 4th sometimes 3rd gear. the truck never saw 6th but only once on flat ground but the truck did not agree with that. The truck ran fine in 5th. My only disappointment about the truck was that if you goosed it alittle to down shift the truck would come out of lock up. I dont like that. The troque converter in our trucks are not effiecent enough for that. So i just used the selector to find the gear that i needed.