Engine components and moving parts wear over time. The right oil can help to prolong the life of your engine. A little understanding of what goes into an oil mix and what it does for your car will help you make the right choices and extend the life of your car's engine.
Oil helps to reduce the friction of the moving parts of your engine and keep it running cooler by drawing heat away from the combustion engine. Specific oils are recommended for the many different types of engines in our world. Passenger car engines are most often classified as light duty. Look for your auto manufacturer's recommendations as to the proper weight (viscosity) of oil to use, and read the oil manufacturer's label on the oil to determine the mix and quality.
Lauren Fix, TV's automotive expert "The Car Coach," says: "It's critical to routinely check the engine oil and transmission fluid to assure they're at the proper level. Have these fluids changed (along with the appropriate filters) at least as often as recommended by the factory under 'severe/heavy duty' conditions."
In addition to following manufacturer guidelines about how often to change your oil, be aware of strange or unusual sounds your car might be making. Fix also warns, "Typically, you'll hear ticking while you're stopped if you're low on oil. Get an oil change as soon as you can."
There is a lot of debate over the use of mineral or synthetic oils in your vehicle. Though Fix prefers the use of synthetics and feels that they wear better and allow more time between oil changes, she also admits they tend to be more expensive. Many longtime drivers feel that mineral and synthetic oils shouldn't be mixed because a synthetic mix may break off a piece of sludge and cause a problem.
Sludge is a black tarry mix that forms when the engine oil is dirty or sometimes when there are leaks into the system. Over time and exposure to extreme heat, the chemicals in the oils break down and cause a sticky, glue-like mixture that does not evenly coat moving parts. Friction builds; metal parts grind against each other; and heat is not transferred away from the combustion case. If the buildup of sludge is too great, or if there isn't enough oil in the system, the engine can seize, and the only possible repair involves replacing the engine.
Motor oils are classified according to both the combination of additives and the viscosity (thickness) of the mix. Viscosity is the measurement of the oil's "resistance to flow." The usual numbers like 5W-40 refer to the level at which the oil thickens in cold weather and thins in hot weather; the number preceding the W is for cold weather. Some owners will winterize -- or "summerize" -- by changing the weight of the oil. There are other number sequences that refer to light-duty engines, severe or extreme use, turbo or diesel engines, or particulate filters.
All motor oils are derivatives of organic or mineral oils. Synthetic blends and fully synthetic oils are careful combinations of refined organic oil and some additives. Some of the more common additives include special engine detergents (to help flush solid particles and lower rust), dispersants (to disperse solids and sludge buildup), anti-wear agents (to "coat" and protect metal surfaces), friction reducers, antioxidants and inhibitors.
Not all engines require these features. Rely on your car's manual to choose the recommended oil. Synthetic blends can handle heavier loads and tend to evaporate less quickly. These are slightly more expensive than organic but don't cost as much as fully synthetic. Fully synthetic oils help to increase fuel economy. Your higher mileage or older car may benefit from the use of a higher viscosity oil or an oil that is formulated to work better for older or semi-dried-out gaskets. Oils made specifically for older engines also have higher rates of anti-wear agents.
Once again, rely on your manufacturer's recommendations for how often you should change your oil and filters. An average recommendation, though, is every 4,000 miles or every four months.