Engine Oil Change Myths, Part 1

Most car owners know that their vehicles will require an oil change to keep everything running smoothly, lubricate the engine, protect the engine from rust and corrosion, and eliminate sludge. Whether the owner understands how, when, and other details about the oil change depends on how much they know about engine oil.

As St. Louis auto service experts, we’ve heard it all over the years. We’re here to set the record straight about the engine oil and oil change myths that our customers often ask about. Here are two oil change myths you might have heard — stay tuned for the final three next week!

Common Oil Change Myths

Dark Engine Oil is Dirty & Must Be Changed

Sludge buildup in an engine is a concern for any driver, as it can dramatically affect your car’s performance. But using the dipstick to check the engine oil color is not the best indicator of sludge buildup, despite the oil change myth that says it is. When your engine oil darkens, it doesn’t mean that it’s dirty and an immediate oil change is needed. Actually, that’s completely opposite from the truth.

Engine Oil Change Myths, Part 1

Most modern engines actually use engine oil with detergent additives. The little particles that can cause engine sludge are dispersed and suspended in the detergent engine oil, preventing build up but causing the oil itself to look dark. The change in color doesn’t do anything to change the effectiveness of the engine oil, though — so it will continue to lubricate and protect the engine from damage.

How can you know when to change your engine oil, then? Be aware of the oil change recommendations of your vehicle’s manufacturer. They should help you determine when your engine oil is saturated and needs refreshing.

The W in 10W-30 Engine Oil Represents “Weight”

This is a misconception about engine oil that we encounter often, perhaps because it does sound logical. But the “W” actually stands for “winter,” not “weight.” Why the seasonal reference? The viscosity of engine oil changes in different temperatures. Viscosity corresponds with the thickness of an engine oil, so that the lower the viscosity, the more smooth the oil runs through your engine, and vice versa. An ideal engine oil will have a viscosity that’s not too high (which prevents even flow) yet not to low (which makes the oil too watery as it moves through the engine).

Viscosity is measured by two methods: single-grade and multi-grade. The most typical single-grade rating is SAE 30, so named because the Society of Automotive Engineers used a standard tube device and timed how long the oil took to move through the tube in seconds. The time is rounded to the closest multiple of 10, meaning that SAE 30 engine oil takes 30 seconds to move through the tube.

An engine oil’s single viscosity rating indicates the oil flow in warm temperatures. Engine oil flows more slowly in the winter due to chilly temps, which means its key to pay attention to your engine oil’s cold viscosity rating as well.

The multi-grade rating of engine oil is the best way to gauge both viscosities to ensure that your oil works well year-round. 10W-30 oil has the same viscosity of SAE 30 warm oil, but the 10W references its cold engine oil viscosity rating. Be sure to keep this in mind when selecting engine oil for your vehicle!

Bust More Oil Change Myths With Waterloo Service

Want more information on engine oil or common oil change myths? Waterloo Service of Waterloo, IL can help you select the best engine oil for your vehicle — call us for more on our services!


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