Driving without an air filter can be a dangerous decision. Without an air filter in place, the engine can suck up dirt and debris, which can damage internal engine parts such as valves, pistons, and cylinder walls. This can lead to excessive oil consumption, poor engine performance, and ultimately engine failure. A dirty engine air filter can cause even more serious problems.
You may notice a reduction in fuel consumption, strange noises coming from the engine, cylinders that fail to ignite, or the check engine light blinking. When the engine can't get the air it needs, it won't work as intended. It's important to keep your air filter in good condition for your health and the health of your car. If you neglect your vehicle's air filter, it can cause a decrease in airflow in the HVAC system.
This will force the system to consume more energy to circulate the temperature inside the vehicle. Over time, this may require maintenance work due to malfunctioning air filters. But even more importantly, it can be a health hazard. Oil bath type air filters from the aftermarket with vehicles that have a massive airflow sensor can be especially problematic.
Oil entering through the filter can contaminate the air mass sensor, which would require regular cleaning with a special cleaner. The filter then requires a special cleaning and lubrication process that, if not done precisely, will send additional oil back to the air mass sensor.