[BabyDiesel]

I did a comparison between speed, instant fuel mileage, and horsepower last night over flat stretches of my route. Being in the coastal plain of NC, we have many miles of flat land.

These numbers are from my calibrated ScanGauge. FE numbers are typically 1-1.5% lower than reported.
Temperature - 73*
Humidity - unknown
Partly Cloudy
SSW wind of 6 mph
Traveling E-SE
Engine temp of 205-215
Results are from after 15+ minutes of driving time

40 mph: 45-47 mpg, 11-12 HRP, 1454 rpm
45 mph: 51-53 mpg, 14-15 HPR, 1636 rpm
50 mph: 47-48 mpg, 17-18 HPR, 1818 rpm
55 mph: 42-44 mpg, 20-21 HPR, 1999 rpm
60 mph: 40-42 mpg, 23-25 HPR, 2181 rpm