Originally Posted by lets blaze
I run about 2500 at 75 or so. damn nowonder I chug fuel
Actually, 2300-2500 is ideal with the OHV 4.0 at that speed (or what ever speed you choose is the optimum highway speed for you). There's a big misconception that you'll get worse fuel mileage as RPM's increase - and that's true to a point. But, in my experience, my truck seems to get better mileage around 2300-2500 rpm....just before the engines torque peek.
If you're still getting poor mileage, I'd start looking for something that could cause it (engine running rich for some reason - skewed ECT, bad O2, etc....)