SIXSLUG

Where are you guys finding the best mileage?

I just got 19.165 mpg heading over to MT for the weekend, hand calced.

I was running around 78 mph and the overhead was showing a pretty decent mpg on the flats. I was around 2200 rpm with stock tires and my gps and the roadside check stations showed my speedo to be right on.

I usually see teh best mileage around 58 mph but that is too slow for a 600 mile trip!!

high bid

Ive found that running about 1900 rpms which is pushing me along about 78mph works pretty well. However, I have run up to 85+ and it just sings along on the hwy. With the recent tranny rebuild overhead monitor is showing 21.5mpg but we all know that isn't accurate. I'm also running 35's so thats a lot of rubber rolling down the road. At 236k miles, I still wouldn't hesitate in driving cross country w/the truck!

KATOOM

Strangely I think that the sweet spot is in two places. Sounds stupid but the two I found are around 55-60 mph and 80-90 mph. Anything in between those figures seems to give the lower more average mileage numbers. The slow numbers are obvious as to why but the faster numbers, I think, are because the engine is running more in the meat of the power curve and overcoming the wind drag until it gets high enough to cause the mileage to drop back down. I say this because, not that I condone driving fast, but one day I had to get somewhere in a hurry and sustained about 80-85 mph for around 100 miles going up in elevation and in the hills, and found my mileage to remain close to 20 but driving 70-75 will almost always give me mileage numbers around 18-19 at best.

SIXSLUG

Good, I'm not crazy. I was also thinking along these lines. The overhead showed higher than expected mpg but I was skeptical until I topped it off with 26 gallons, allowing the foam to settle twice before calling it quits as I usually do.
Also, my trip gets some altitudes and we know how they like that....