The goal of motor oil is to protect and extend the life of the car’s engine. Vehicles with internal combustion engines, such as cars, require oil to lubricate its many moving parts as well as to clean and inhibit any corrosion. It further cools the engine by carrying the heat away from the critical moving parts and also improves sealing.

Within car engines, there are numerous parts which make contact with each other and cause damaging friction. Not only does this friction wear away at those parts involved, it wastes the beneficial power created by such and instead creates heat, which in and of itself can be damaging. This contact ultimately leads to the degradation of the engine and lower efficiency overall. And, these detriments further go on to decrease fuel economy and power output, with the potential for engine failure.

The main role of motor oil is to create a film between these parts which minimizes heat. The motor oil is the vehicle by which the heat is transferred elsewhere, in simple terms. Oil also coats the many metal parts and prevents their exposure to oxygen, preventing rust and corrosion.

Detergents and Dispersants: Motor oils often have detergents and dispersants added to better keep the engine clean and minimize oil sludge build-up. This is achieved by the oil primarily trapping the soot from the combustion and moving it away from fragile internal surfaces.

Oil Filter:  Running of metal parts produces some degree of metallic particles, though microscopic in size, from the wearing of the surfaces which is inevitable. These particles, even if minimal do impact the surfaces of which it comes in contact by grinding. Oil is passed through an oil filter which serves to remove harmful particles.

Viscosity or Weight Levels: When having your motor oil changed, you are bombarded with choices; the most critical is that of grade or weight. Years ago, oil was sold in single grades but cars are so advanced now and there are other considerations. Now, oils can be purchased in multi-grade, which means it has two weight ratings. The format of multi-grade oil is XXWXX, with the “XX” indicating a variable number; for example, 10W40. The first number refers to the weights of the oil at cold start-up and the second number refers to the oil weight after the engine’s operating temperature is reached

In order to understand what kind of motor oil that your vehicle requires, we must discuss the basic notion of viscosity. Viscosity is essentially the “weight” or even “thickness” or a measure of its resistance to flow. The viscosity of a particular oil must be high enough to maintain a lubricating film, yet sufficiently low so that it will flow around the engine parts under all conditions that might be experienced. To further explain, low-viscosity oils flow easily at low temperatures which high-viscosity oils flow slower at the same temperature. Low-viscosity oils make cold-weather starting easier and reduce friction in cold engines while the higher-viscosity oils maintain better strength and pressure at high temperatures and heavy loads.

Most oils available today are multi-viscosity such as 10W30 or 20W50. In general, the lower the first number, the better the oil will perform in extremely cold conditions. Conversely, the higher the second number the better the oil will protect at higher temperatures.


Changing the oil in your car every 3,000 miles was necessary in the 1970s, when most cars used 10W-40 oil, which tended to wear out within about 3,000 miles. As cars age, the bearing surfaces wear and create larger gaps between the bearings and their surfaces. The seals and gaskets tend to dry out, crack and ultimately fail as well with time. Thanks to improvements in high-quality lubricants and tighter tolerances in the assembly of automotive engines, the 3,000-mile baseline simply does not apply to many cars on the road today. In fact, automakers now recommend that you change oil at 5,000, 7,000, 10,000 or even as high as 15,000 miles for newer models under ideal driving conditions.

Unless you’re driving a car that’s more than ten years old, or under super extreme conditions, there’s really no reason to change your oil at 3,000 miles anymore. Severe use involves extensive idling or driving frequently in stop-and-go traffic; operating in cold temperatures below 10 degrees or extreme temperatures above 90 degrees; extreme humidity; repeated short-distance trips of less than five miles; towing a trailer or hauling heavy materials; or using E85 fuel more than 50 percent of the time. If you do drive in any one of these conditions in a typical week, you are driving in severe conditions, and may need to change oil more often.

If you are an extremely low-mileage driver, you should change your oil at least once a year. Otherwise, if your vehicle is equipped with an Oil Life Monitoring System, you can trust the info/alert on your dashboard to tell you more accurately when you need a change. Don’t have an Oil Life Monitoring System? Consult your owner’s manual, your auto manufacturer’s official website, or authorized dealer for more information.

Curious about your car right now but don’t have an owner’s manual handy? Check out to many makes and models to determine when best to change your oil.


We hope you enjoyed this post. If there is anything else we can do to help you feel free to call us at (805) 466-2446 (Atascadero) or (805) 239-8752 (Paso Robles). And be sure to stay connected with us on Facebook as well!