The RPM does not necessarily correlate to fuel consumption.
Think of it like this.
You are traveling at 55 mph.
With no down or upshifting during this exercise, you encounter a slight uphill grade, and you begin to decrease in mph.
What do you do to maintain a constant 55 mph?
You increase the fuel consumption! More pedal!
More fuel equals more power.
The same applies to large scale diesel generators, where increased RPMs, could be detrimental to the generator's windings from centrifugal force.
These engines are governed to a specific RPM and a fuel rack dispenses more fuel when a load arises maintaining a constant RPM.
I hope this helps some understand the dynamics of fuel consumption at specific rpm a little better.
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Rusty
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