Ask The Experts at K&N How To Use K&N Air Filter Oil – How Much Oil Do I use? K&N uses much more scientific methods of proving that K&N replacement air filters outperform their disposable equivalents. Ask The Experts at K&N How To Use K&N Air Filter Oil – How Much Oil Do I use? Read more about Ask The Experts at K&N How To Use K&N Air Filter Oil – How Much Oil Do I use?