We may not know how to replace the brake pads or even how to change a flat tire, but almost all drivers know how to add oil to their vehicle. You just pop the hood and pour some in, right? Well, not exactly. In order to protect your engine from premature wear and tear, you must use the recommended motor oil.

To find out what you need, simply check your owner's manual. In most instances, it will tell you to use either a synthetic or conventional product. The former is generally needed for high-performance vehicles, while the latter offers sufficient protection against heat buildup for most other automobiles. There are also synthetic blends for vehicles that carry heavy loads, such as trucks, vans, and SUVs.

What About Viscosity?

If you follow your owner's manual to the letter – and you should – it will instruct you to use a specific viscosity grade, or thicknesses, of oil. Because different engines run at different temperatures, different grades are needed to prevent overheating. Their thickness and suitability is determined by a series of numbers. The most common ones are 5W-30 and 10W-30. What do these numbers mean?

Measured by the Society of Automotive Engineering, the numbers indicate the fluid's thickness during hot and cold testing. For 5W-30, the first number (5) is the oil's thickness when the motor is cold, and the second number (30) is it's viscosity when hot. Because thinner grades put less strain on the motor, they are preferred when heat is not an issue. Conversely, a thick fluid provides much-needed protection when temperatures rise. As such, the grade you need depends on how hot your engine runs.

Is It Really That Important?

Yes, it is really that important! Using the wrong type, or even grade, of product can result in permanent damage to vital engine parts. This is especially true if you own a vehicle that requires synthetic motor oil, but you mistakenly use a conventional one. What could very well happen in this instance is that the natural motor oil would break down under extreme heat, causing inadequate lubrication. With lubrication lacking, friction between moving parts could easily cause serious, even irreparable damage. More than a few motorists have blown their engines because they used the wrong fluids.

Voiding Your Warranty

Even if your vehicle is still under warranty, damage that occurs because you used the wrong motor oil may not be covered. It is also possible to void your warranty if you use a fluid that is too thick or too thin. There are even cases where automakers have refused to cover damage attributed to a non-approved fluid. To avoid this unpalatable scenario, make sure you always use a liquid that has been approved by the Automotive Petroleum Institute (API). You'll know it by the "sunburst" logo that always appears on labels of approved products. So, if you do not see that sunburst, do not buy or use the product.

As the lifeblood of your engine, the right motor oil can keep your vehicle running smoothly for years to come.