Its amazing how efficient these trucks run in that 50~60mph sweet spot. I get similar numbers have seen as high as 24 a few times on the rural 2 lane roads.. hit the interstate and 75~80 it all goes out the window... still not bad 19~20 steady state.. but as Sammy says.. I cant drive 55....
60-MPH is reference for a variety of collected data.
In FE it’s that aerodynamic resistance becomes a wall increasing on the square. After 65 there’s no such thing as
economy as it’s been relegated out. Tire wear, engine wear, etc.
This is for any vehicle.
As a CTD is expected to work (and is an unstable platform reflecting design compromises made for manufacturer and operator convenience), think of it as
55-65/MPH capable. Handling is such that it’s rollover prone empty or loaded.
With the above in mind it’s easy to maximize available TQ in the expected top range via axle & trans gearing plus tire height, etc. 4-whl disc w/ABS is the other part. Throttle & Brake Response are such that one can push along in that speed envelope without much concern.
One initiates momentum and allows it to build on departing a stop. Up into the favorable rpm cruise range not much throttle
change is needed to maintain that headway.
Steady State RPM is king.
Seen over a very long distance it’s that a
glide has been established where we don’t want external conditions to intrude any more than necessary (keep separate from traffic so as to more easily deal with road, load and weather).
Under 60-MPH is where we’ve separated ourselves from wind pressure
and are above the rolling resistance factor below 45-MPH. The national speed limit of 55-MPH wasn’t a random choice as it worked from both those factors.
Fuel Economy for a given trip is one thing.
Long term economy is in least fuel plus tire wear, etc, to keep the vehicle at highest reliability & longest life stress-level.
Fuel burn — versus what’s possible at 60-MPH — is the percent degradation divisor overall when
wind resistance comes into play.
High compression flattens grades.
Turbocharging means a higher average MPH.
These trucks are already overpowered.
Pushing past design limits
doesn't pay.
We lose the leverage of the money we can’t get back.
That’s a double penalty.
.