Regardless of whether your car's engine has a carburetor or fuel injection, whether it is powered by gasoline or diesel fuel, one item it must have is a clean air filter. Just as an athlete wouldn't run a race with a sock in his mouth, a car shouldn't run with a clogged air filter.
Oxygen is essential for proper fuel combustion in the cylinders. If you notice reduced engine performance, especially at high speed, your air filter may be dirty. A clogged filter will also reduce your gas mileage. You should inspect the air filter every time you change the oil. You should be able to see bright, such as sun light through the filter at all points. If you cannot, it should be replaced. If the filter is only slightly dirty, you can try cleaning it by tapping it on a flat surface or by blowing compressed air through it, from the clean side out. You'll find that you need to replace your air filter more often if you frequently drive on dirt roads or live in a dusty area.