Quote:
Originally Posted by thefoos
Engines are most efficient at peak torque rpm 
That is why old stock V8's are most efficient at low rpm. They are cammed/tuned for low rpm torque |
Most Efficient has nothing to do with fuel economy. The engine may be breathing most efficiently at say 4000 rpm. However FE means least amount of fuel used. IE gal/hour or liters/hour.
Any engine management system today will always try to keep A/F ratio to 14:1. Therefore if you accelerate at WOT or even 1/2 WOT you are using a large amount of fuel far more than saying driving with an egg on the dash method(grannie driving).
I have a scangauge on my vehicle. If I accelerate at even 1/2WOT I am consuming rate of at least 4-5 gal/hour. However if I grannie the gas pedal I am consuming at 1.5 to 2 gal/hour.