Changing an automobile air filter is one of the easiest DIY projects out there. Not to mention, a clean air filter will significantly improve gas mileage. Step one, find the air box in the engine compartment. This is usually a black plastic box (not necessarily square) that has a large plastic/rubber hose(3’+ in diameter) running from it to the top of the engine. There are usually there are easy to remove clips holding the air box together, undo these and open it up. Inside you will find the filter. Remove the filter, taking note of how it was placed in the air box. Put new filter in, and close the box.