3g hemi gas mileage

I think you have 2 much gear i went from stock 2.82 gear to richmond 3.55's in my 06charger and lost about 5 mpg the car weighs 4272lb. The car was alot faster but ending up with 3.06 getrag gear. not sure about the tire diamiter but they were the 08 up alcoa srt wheels 255 45 20 f1 tires should be taller than will fit on a a body