I call B.S. If your engine operates at peak efficiency at 1800-2200 RPM and you have a 6-speed manual transmission, you will achieve higher mileage in 5th gear than at the same RPMs in 6th. Aerodynamic drag is not negligible at speeds over 60MPH, and it increases exponentially.
I innocently entered "Secant Tangent Cosine Sine 3.14159" into WolframAlpha. The result, 74.69263, now belongs to Wolfram. Sorry about that.
... until this shows up on the Colbert Report.
I call B.S. If your engine operates at peak efficiency at 1800-2200 RPM and you have a 6-speed manual transmission, you will achieve higher mileage in 5th gear than at the same RPMs in 6th. Aerodynamic drag is not negligible at speeds over 60MPH, and it increases exponentially.