Over the winter, your car's air filter can get clogged with salt and other thick debris. A clogged air filter can really lower your fuel efficiency. Replacing a dirty or clogged air filter can improve gas mileage by as much as 10 percent
But how do you know when to change your air filter? The recommended interval is every 12,000 miles (19,312 kilometers), but that can be affected by the particular road and air conditions in which you drive. If you do a lot of driving on dirt or gravel roads, then your air filter is going to clog up much faster than an air filter in a vehicle that's used strictly for highway driving. The only real way to know if you need to replace your air filter is take it out and give it a quick inspection.