A vehicle’s rear axle ratio is numerically expressed. A higher number denotes a lower ratio. For example, if the axle ratios were listed as 3.31:1 and 3.42:1 and 3.55:1 and 4.10:1, the lowest ratio of the four gears is 4.10:1. The lower the gear ratio, the more rpm required to maintain a given speed with equivalent tire sizes.
While the gear ratio will have an effect on the actual fuel economy of your vehicle, your driving habits will offset any gains or losses. The actual difference between a 4.10 gear ratio and a 3.73 gear ratio at highway speeds is less than 200 rpm. At less than 60 miles per hour, fuel economy is primarily dependent on driver habits, rather than gear ratio. To lower your fuel consumption, drive at a consistent and moderate speed.