When checking an air filter, it's important to remember that if the filter is working properly, it will have some dirt on it. The trick is to know when it is dirty enough to be replaced. The best way to do this is by holding it up to a light, if the light can pass through the filter then it is likely that air can pass through it. Some other key indicators are black smoke from the exhaust, rough engine noise and poor fuel economy. We recommend that you check the air filter whenever an oil change or service is being carried out. For more information,
see our guide on how to check your air filter.