i don't think any of the air/fuel products really work and yes that includes the K&N filters. you have to remember the air/fuel are now cpu controlled. it's what limits how much and how fuel. if sent to engine. that's not to say that they don't on some cars i.e. older carb cars that are not cpu controlled. but thier are orther ways to increase fuel/mpg. like maybe better spark plugs and yes lucas oil. the engine does control how much spark or how much lube. so better spark means better use of fuel. also better lubericant means less friction. altelast that's my opinion