
While I'm not sure how much my mileage has increased, I've had 3 upgrades in the same week with new ones Tires installed, the cooling air intake and edge tuners. Together they increased my highway mileage on my 2006 Chevy Silverado 2500HD from 11 mpg highway to about 18 mpg. Installation was easy and over time even a 1mpg increase for this upgrade would have paid for itself.

π K&N Cold Air Intake Kit: Rev Up your 1998-2003 CHEVROLET/GMC (S10 Pickup, Sonoma) with High Performance: Gain Horsepower & Stay Road Legal (57-3025-1)
9 Review

π aFe Power Magnum FORCE 54-12092-1 Jeep Wrangler (JK) Performance Air Intake Kit (Oiled Filter, 5-Layer Filtration)
9 Review

π Enhance Your Vehicle's Performance with the Airaid 200-919 M.I.T. Modular Intake Tube.
9 Review

69 1018TS Performance Intake Kit
9 Review