Motor Oil 101 – What You Need to Know

2019/04/17

Whatever vehicle you drive, you might get an oil change every 7,500 to 15,000 km, but what exactly does motor oil do? What is motor oil made of? Why do you need a regular oil change? Here, we’re covering the basics of engine oil functions, composition, how it wears out, and why you can’t skip oil changes.

Motor Oil Function

You’d be correct in mentioning engine oil’s primary function, lubrication, but it also serves as a hydraulic fluid and coolant. As a lubricant, engine oil forms a thin film that, even under high pressure, keeps moving metal surfaces from contacting each other. This reduces friction and wear.

As a hydraulic fluid, engine oil is used to pressurize various engine components, depending on the design. Most variable valve timing (VVT) and variable valve lift mechanisms are controlled using oil pressure. Zero-lash hydraulic lifters also rely on oil pressure.

To a lesser degree than engine coolant, engine oil functions as a coolant, removing heat from some of the hottest parts of the engine, such as the pistons and cylinder walls. Moderating engine temperatures improves engine performance and reliability.

Motor Oil Composition

Engine oil, no matter what weight, viscosity, blend, or brand, is made up of two basic components, a base oil and an additive package. Base oils can be mineral-, synthetic-, or vegetable-based, or any blend thereof. Mineral oils are refined from petroleum deposits. Synthetic oil is chemically synthetized from other chemical bases. Vegetable oils or bio-oils can be refined from plants. On its own, these oils are good lubricants, but there’s a lot more they could do.

The additive package varies, depending on brand, application, type, and a host of other factors. In fact, we could dedicate several articles to just engine oil additives, but here’s the gist of the story: Oil additives enhance good oil properties and suppress undesirable properties. For example, anti-oxidants slow oxidation and burning, while corrosion inhibitors improve rust protection inside your engine. Anti-wear agents bond to metal surfaces, reducing friction, and detergents isolate soot particles to be captured in the oil filter. The additive package makes up 10 to 30 percent of the oil in every litre, and what we worry about when talking about regular engine oil changes.

Motor Oil Wear

Engine oil doesn’t wear out so much as burn up. True, base oils tend to last a long time, but the additives don’t. In enhancing your engine oil, they burn off or evaporate, leaving behind the base oils.

Depending on how you use your vehicle – short trips and stop-and-go traffic are the worst – this can happen in as little as 5,000 km. Reducing overall engine oil volume, by 10 to 30 percent, the leftover base oils tend to overheat and oxidize quicker. That’s right, this means oil sludge, which can clog oil passageways. Running like this, the engine can quickly destroy itself, resulting in complicated and time-consuming repairs.

No matter what your automaker recommends for an oil change interval, it pays to check and adjust oil pressure at least once a month. If the oil level goes below the safe marking, add the correct motor oil to bring it to the full line. Be sure to use a quality oil and new oil filter at your next oil change. To help your engine last longer and perform better, get an engine oil change on time, every time.

Check out the oil change services available at any of our 600 NAPA AUTOPRO locations for routine maintenance and repairs. For more information on motor oil, chat with a knowledgeable expert at your local NAPA AUTOPRO Service Centre.

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