I have larger tires on my truck and they give an increase of about 5% + or-.
I am either covering more ground at the same revs or turning fewer revs at any given speed. I guess it depends on how I want to look at it. Either way it is a plus. I will continue to run larger tires. I have been getting about 28 mpg in the truck by the odometer, but the real mileage is about 30!
Go for it!