related linksRead more advice-related articles
MORE ON MSN AUTOS
MORE ON MSN
MSN AUTOS VIDEO
Re: #5... a dirty air filter won't affect economy... DISPUTED (especially at open throttle).
Certainly, modern sensors and computing power can respond to slight additional restriction, and deliver a proper air/fuel ratio. And every modern engine uses some form of resonant airbox tuning to flatten divots in the open-intake torque curve, so the intake is already semi-closed. Yet the engine still must "suck" harder against that constant, if slight, additional intake restriction to fill its cylinders.
There can be no free lunch. Increased intake restriction causes additional pumping losses, i.e. it takes just a little more oomph to turn the cranktrain over against that incrementally tiny greater friction.