Original BMW i3 air filters come from the factory the best means of keeping contamination out of your engine parts and HVAC system. Engine air filters catch it before it can gunk up your throttle body, carburetor, or other auto parts. Cabin air filters capture it before it gathers in and on your heating and air conditioning ducts and vents. Even high-quality air filters eventually clog or break down. Engine filters with too much buildup can raise your air-fuel ratio and result in engine inefficiency, lower fuel economy, higher emissions, and even engine misfires. Cabin filters full of crud can cut airflow through your heater and AC, resulting in irregular interior temperature, poor cabin air quality, and even more stress than normal on your motor. When to change engine and cabin air filters is simple. A Check Engine light might let you know; do an inspection first to figure out if that's true. Brittle fibers, discolored filter surfaces, and dirt and debris pile-up are better symptoms. Other signs of engine filter problems include unusual engine noises or too much exhaust production. Other signs of air filter problems range from unclean smells to bad airflow. Check your owner's manual for a filter replacement schedule. Which air filters best fit your BMW i3? When in doubt, go genuine. OEM air filters are designed compatible with your model, making them the most reliable. Order yours online today from our auto parts counter -- we ship quickly, right to your door!