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DouglasABaker · 13th October 2008, 18:32

The bottom line in all of this is that without having an efficiency vs. rpm curve for the engine, we're all sort of guessing.

Without the charts from BMW (or someone developing them independently) there really are too many variables to talk about what speed is most efficient.

We do know, however, that there is no issue with running the engine at any rpm in any gear, so long as the vehicle is making sufficient torque for the situation. 30 mph in 6th gear, for example, is fine on a flat or down a hill, but may not be ok going up a hill (depending on steepness). 2000rpm is fine pretty much regardless of situation or gear given the hp available.

d-

13th October 2008, 18:32	#9 (permalink)
DouglasABaker M5 Guru (>2000 posts) Join Date: Jan 2007 Location: Franklin, MA Age: 35 Posts: 3,347 Blog Entries: 5 Thanks: 41 Thanked 711 Times in 328 Posts	The bottom line in all of this is that without having an efficiency vs. rpm curve for the engine, we're all sort of guessing. Without the charts from BMW (or someone developing them independently) there really are too many variables to talk about what speed is most efficient. We do know, however, that there is no issue with running the engine at any rpm in any gear, so long as the vehicle is making sufficient torque for the situation. 30 mph in 6th gear, for example, is fine on a flat or down a hill, but may not be ok going up a hill (depending on steepness). 2000rpm is fine pretty much regardless of situation or gear given the hp available. d- Last edited by DouglasABaker; 13th October 2008 at 18:36.