I was asked this very question today – After showing the customer the black soot, bug, and grime encrusted air filter from their LAND ROVER. I could not believe they questioned me on its replacement. Air filters need to be changed – OFTEN! Dirty air filters restrict the air flow to the engine, which makes the engine work harder and less efficient as well as creating excess wear and tear. How do you work when you can’t breathe? Dirty air filters waste fuel and then your fuel economy plummets – costing you more $ at the fuel pumps. Have your air filter checked at every oil change. Replacing a dirty air filter is inexpensive to replace, but will save you big money in the long run!