from what i know is there is a sweat spot in your rpm(use your ears you know when its happy) my chevy picked up milaege when i went from 3.23 to 3.73, was no longer boggy at 60 and had more power, just take what speed you averenge and know where you want to be, like my i like 18-1,900rpm, above 2 and i'm wasting fuel, find me in the slow lane in the morning. 55 and stay alive

 

OK so final thought on this one. Obviously if your around town 4.11 works best or if your drag racing. For mileage what Im seeing is this. The best combinations are ither 3.55 with the stock tire size or 3.73 with bigger tires. Plus the bigger tires are cheaper than changing your ratio.

 

Or a gear vendor.....

 

Best option IMO