The air filter in your vehicle can serve some important purposes. This is because it filters debris out as it comes under the hood of your vehicle, helping to prevent this debris from getting into the engine or other parts that work with the engine. Debris can cause a lot of problems, such as clogging intake valves. Burning debris in your vehicle can also be dangerous. As useful as these filters are, you should keep yourself up-to-date on when to change them. Here are some signs to look for.One sign that your filter may be getting old is that you may notice your gas mileage decreasing. This is because the engine has to work harder if the airflow is restricted by a lot of debris in the filter. Although it probably won’t be obvious at first, it can start to get worse the more clogged your filter gets.Another sign that it may be time to change your air filter could be that you are having problems with your ignition. This could be caused by debris getting into your spark plugs, which prevents them from sparking and causes your ignition to have trouble starting. You’ll notice this if your car doesn’t start immediately or if it is relatively slow to start.Even if you may not necessarily notice signs that it is time to change, it’s safer for you to go ahead and change it during the recommended times before it has the chance to start negatively affecting other parts of your vehicle. Your owner’s manual should have instructions for how often to get your filters changed, but if you drive around in a dusty location, you may need to change it more often. You can also visually look at the filter if you know where it is and how to take it out to check it. It should be white or off-white, but if it is full of debris, it will start looking dirtier or even turn black.When you suspect you may need to change your air filter, you should take your car to a professional to have the job done. Professionals have the training to know which one to use for your specific car as well as how to remove the old one and replace the new one correctly. Getting the job done by a professional may reduce the risk that something is done incorrectly.