It’s amazing how many guys will faithfully go to the gym three times a week yet let their car or truck go for months (sometimes years!) without replacing the air filter or oil filter. While there aren’t hard and fast rules dictating exactly how often you should swap out your filters because it varies by driving conditions and the number of miles you log, there are some guidelines you should consider. After all, just like a good workout, a shower or a haircut, your vehicle needs regular maintenance to function at its peak.

An engine’s primary defense against internal abrasion, and the resulting wear and tear, is the oil filter. Oil filters, like K&N oil filters, remove solid contaminants like dirt, carbon and metal particles from the oil before they can damage the surfaces of bearings, journals and cylinders within the engine. The fresher the filter, the more effective it is at trapping these contaminants.

In modern engines, oil is routed through the filter before it goes to the crankshaft bearings, cam bearings and valve train-gear heads call it “full-flow” filtration. It’s the most efficient way of removing contaminants, assuring only filtered oil finds its way into the engine. As the filter begins to wear, it develops buildups of dirt and debris that obstruct the flow of oil. To maintain performance and prevent engine damage, the filter should be changed before it reaches this point. Waiting too long can result in engine failure due to loss of lubrication and catastrophic damage to your engine.

Many auto manufacturers will tell you the oil filter only needs to be replaced at every other oil change, but with modern vehicle’s this isn’t sufficient. Today’s oil filters have been downsized to save weight, cost and space. What was once a quart-sized filter has been replaced by a pint-sized filter (a pint being smaller than a quart). Obviously, this reduction in size provides less total filtering capacity. Nevertheless, these smaller oil filters should easily stand up to about 3,000 miles, but they won’t make it past the 6,000-mile mark. Replacing the oil filter every time the oil is changed is probably a good idea to maintain the best possible engine integrity.

Regularly changing your air filter is just as important. When air is restricted, your engine can fail, leading to overheating and even a cracked block. Even worse, when airflow drops, your ride has to use more fuel to make the same amount of power, so your MPGs are going to tank. The life of an air filter depends largely on how much crud it collects. Believe it or not, a slightly dirty air filter actually cleans more efficiently than one that’s brand new. That’s because the debris trapped in the air filter screens out smaller particles. Eventually though, every filter reaches the saturation point, causing a noticeable pressure drop that restricts airflow. Fuel economy, performance and emissions erode and continue to suffer until the dirty filter is replaced.

In general, a quality air filter will last between 20,000 – 30,000 miles on a vehicle that sees mostly freeways and major side streets-city driving in other words. Be prepared to change it more frequently if your driving conditions contain poor air quality (we’re looking at you, L.A.) or take place in a rural setting, with dusty roads or other airborne contaminates. In this environment, air filters, like a K&N air filter or Infiniti G35 air filter, may perform effectively for only a month or two. Perform a visual inspection of your air filter every 10,000 to 12,500 miles. If it still looks OK, pop it back in and check it when you hit 20,000 to 30,000 miles of use.