You can find the air filter casing on the left side next to the front of the engine space. First remove the inlet air duct from the G35 model engine compartment, then untwist two clips that hold together the air filter housing's two parts. First, remove the filter by undoing all fasteners on the inlet duct, pushing away the clips, breaking open the housing's two sides, and pulling out the filter. First, look at the outside of the filter element. If it's significantly dirty, buy a new one. But if it's just lightly coated with dust, you can resuse it - blow away dirt from the back to the front by using compressed air. Because the filter is made of pleated paper, you cannot wash or treat it with oil, and if it's too dirty to clean right, you need to get a new one. When taking off the cover, watch out for anything falling into the filter space by mistake. Always have a functioning air cleaner when driving, as driving without it causes too much stress on the engine and might start fires. Dust off the filter case, then put the fresh filter into its space while making sure it fits exactly. Close the housing again by doing the removal steps in reverse order.