Knowing when to replace an air filter in your car is important if you want your car to perform well. However, if you do not want to waste your money, it's important that you don't replace it too early. While there is no absolute time to change an air filter that applies to everybody, there are certain things to consider when deciding if your air filter needs to be replaced.
Driving conditions can greatly affect how often an air filter needs to be changed. A car that is driven mainly on clean, modern, well-paved highways will most likely require a later air filter change than a car that is driven on dusty, sandy, old, gravel-filled roads. Air quality is an important determining factor in your air filter's condition.
A general rule of thumb is to perform a visual inspection of your air filter and clean it every 10,000 to 12,500 miles. Most of the time, an air filter will not need to be replaced at that time, unless the driving conditions are unfavorable. Once your filter hits 20,000 to 30,000 miles of use, you should check it again and be ready to replace it. Some air filters may last until 50,000 miles of use or more, but you should never wait that long to inspect your filter.
Be familiar with your usual driving conditions, and assess how those conditions may affect your filter. Be ready to change it more frequently if your usual drives involve poor air quality. Air filters that are regularly checked and cleaned every 10,000 to 12,500 miles will generally last longer than those that are not routinely checked. So, be responsible with your vehicle to maintain a properly performing air filter. Otherwise, your air filter's performance many decline, along with your car's engine and mileage.