How to Tell If a Car Air Filter Needs to Be Changed

1). Determine when the air filter was last changed, if possible. Check your service records or ask the previous owner (if you just purchased the vehicle). Under normal driving conditions, air filters last approximately 12 months or 12,000 miles.
2). Turn the engine off and open your hood. Locate the air filter assembly to visually inspect the air filter (the filter compartment is usually rectangular and about the length of a loaf of bread).
3). Flip the latches securing the top part of the air filter assembly. Open the compartment and lift the air filter.
4). Visually inspect the filter. Unless it's brand new, it's likely to be a little dirty; but if the filter is extremely dirty, it probably needs to be replaced.
5). Shine a flash light to the filter. If the filter is so clogged that light is barely visible on the other side, consider replacing it.