Big debate between the commentary team for the Xfinity race in September 2020. A spotter or crew chief radio call said they were trying to run competitors out of fuel by running the highline.
This was almost immediately quashed by the commentators, Dale Jr, Jeff Burton and other. The argument being the lap time on the high line was the same and the throttle was flat for the same amount of time ergo, the fuel used was the same at the top and the bottom.
But I beg to differ. The top line is the furthest way around the track.
If you travel more distance you must use more fuel, regardless of the lap time regardless of having the throttle flat.
The difference in fuel economy comes from the RPMs the car is running. If it travels a greater distance in the same time the car must be travelling faster in the top line which means the car is turning more RPM for a lap which means it burns more fuel.
Is the difference enough to make a difference? That I don’t know.