If you want to do it, just do it. No need to make up some pretense about it being better for fuel economy.

If you really want to know, well, Ford designers knew what they were doing. Even if you did improve fuel economy, the fuel savings would never pay for 10% of the cost of the upgrades. Aftermarket rims could make the car lighter, but wider tires could add drag, and a bad offset could throw off handling and add drag there. An open exhaust could save a slight amount of fuel but annoy your neighbors.

Best thing you can do for fuel economy is drive sensibly. Lighten up your right foot.

You could lower it,but putting retarded looking big wheels will kill your fuel economy.Rolling resistance.