The air filter prevents anything floating in the air from entering the engine. This stuff, like dirt and dust, can damage your engine. It’s only $5-30, and we recommend getting it replaced yearly. Otherwise, anything could get sucked into the motor like leaves, bugs, water, and damage the cylinders and valves in your engine.
The fuel filter is similar to the air filter in that it keeps dirt and rust from entering the fuel. It should be replaced every two years or 30,000 miles, but you can go longer on a newer model. A telltale sign that you need to get it replaced is when your mechanic does a fuel pressure test and the pressure is lower than normal (below 30 to 60 PSI, model-dependant). This is one of the things that, if kept unchecked, can lead to your car breaking down on you. Some symptoms of a bad fuel filter is a sputtering engine, a rough idling engine, less power of your car, poor gas mileage, the Check Engine light, or the car failing to start.
Replacing these filters regularly will keep your car in peak condition. You want to replace your air filter annually, and your fuel filter biannually, to make sure they don’t start letting junk into your car.