Review on K&N Engine Air Filter E-0945: High Performance, Premium, Washable Replacement for 1995-2017 Ford Super Duty V8/V10 and Mustang by Paul Williams

Previously, after a full adjustment and all fluid changes, about 90% of highway driving, my 1998 Ford Expedition Eddie Bauer (5.4L, 4WD) achieved 15.3mpg. The ONLY thing I changed was putting this thing in the airbox. As a result, I'm now averaging 16.6mpg over the same route, in the same conditions and with the same fuel. Can't say for sure if that's extra horsepower or not - it's a big old SUV, not a sports car - but it will pay off in fuel economy alone, with the amount of miles I drive each day. Definitely worth buying.