This debate is suffering badly from lack of data, and lack of new arguments. Everyone seems to be going back and forth with the same stuff. So, I googled it up, and found lots of information on another hypermiling forum. I'll post it in chunks to make it easier to review and respond.
MetroMPG, the guy whose test is being used as an anchor of the anti-WAI argument, insists that his test is only valid for his vehicle:
http://ecomodder.com/forum/showthrea...rence-529.html
...also, he continues to run the WAI in spite of that test, because of the warm-up gains:
http://ecomodder.com/forum/4225-post11.html
That's because of his own tests not regarding steady-state driving:
http://ecomodder.com/forum/showthrea...iment-432.html
His own testing shows that it does increase FE even on
his car, just not during steady-state driving.