[joema]

Hey All!

I must be the worst back yard mechanic in the world! I can't figure out why, on a modern engine, a dirty air filter should affect mpg. Conversely, why should a K&N filter improve mpg?

Don't modern engines control fuel/air mixture? If a filter passes more air at a given throttle setting, doesn't fuel flow increase. How does more gas, which results in faster acceleration, improve mileage? From what I can see, it's more likely that a dirty filter will improve mpg.

The only way I can see a K&N filter improving mpg on a modern computer controlled engine is if it somehow 'fools' the computer. Does the MAFS get fooled? Maybe the engines are set up to run at a air/fuel range instead of a hard target. Maybe, then, a change in air flow through a filter, can let the engine run richer or leaner?