1. Engine Oil
Why: Without an adequate supply of clean oil, your engine will wear more rapidly and could even seize and be destroyed.
When: Change your engine's oil and oil filter at the intervals specified in your owner's manual, and follow the more frequent "severe service" recommendations if your driving habits meet any of the conditions described therein.
2. Antifreeze/Coolant Protection
Why: The primary task of engine coolant is to transfer heat from the engine to the radiator, where it is removed by the passing airflow. It also prevents the cooling system from freezing and protects the engine and cooling system from rust and corrosion.
When: Check the coolant level at every oil change. Have the system flushed and refilled with fresh coolant at the interval specified in your owner's manual.
3. Windshield Wiper Blades
Why: Windshield wipers are easy to overlook until you find yourself in a pounding rainstorm. If your wiper blades are worn, cracked or rigid with age, they will not adequately clear your windshield.
When: Check your car's wiper blades at each oil change or whenever they fail to wipe the glass clean in a single swipe. The lifespan of a typical rubber insert is six to 12 months.
4. Tire Tread
Why: The four points where the rubber meets the road are the only things that stand between you and an accident. On wet or snowy roads, having good tires with sufficient tread depth is crucial, as it reduces the likelihood of hydroplaning on wet pavement or losing traction in the snow.
When: Check the tread depth of your car's tires whenever it appears low. Insert a penny upside down into a tire groove. If you can see above Lincoln's head at any point, replace the tire.
5. Tire Pressure
Why: Over-inflated tires ride roughly and suffer premature wear at the center of their tread. Under-inflated tires decrease fuel economy, cause imprecise handling, suffer premature wear at the edges of their tread, and can overheat and fail at highway speeds.
When: Check the tires' pressure (including the spare) at least once a month when the tires are cold. Always follow the inflation pressure recommendations in your owner's manual, or those on the tire information label that is located in the glove box or on the driver's doorjamb—not the inflation pressure molded into the tire sidewall.