[Panther140]

Yes, that will help you gain mpg. Gasoline engines produce their best brake-specific fuel consumption numbers when with WOT and an operating speed at/near the RPM at which the engine makes peak torque.

Another trick you can do is to coast down hills, accelerate hard while going up them. That way, your vehicle gains potential energy efficiently because it is WOT. It is more useful to go WOT while up hill, because you gain potential energy without encountering a large amount of wind drag. You can start at the bottom of the hill at 40mph, floor it until you are going 60mph, and then coast for a mile or so down the other side of the hill without a high peak velocity that would cause much wind drag losses.