What Do Oil Grade Numbers Mean?

Motor oil grades are numbers that represent the viscosity of motor oil. The lower the number, the less viscous (thinner) the oil is. For example, straight grade 30 weight motor oils are more viscous than straight grade 10 weights.

In this blog post by Cutter Mazda Honolulu, we’ll talk in detail about the motor oil grades.

What do These Numbers Mean?

Typically, motor oil grades range from 0 to 60. The lower the number, the lighter and less viscous the oil is.

The most common grades in everyday use are 10W-30 or 10W-40. These numbers tell us that it’s a straight-weight oil that behaves like a light 30 weight or 40 weight oil at operating temperature.

The “W” stands for winter, meaning that it’s suitable for cold temperatures ranging down to -35°C (-31°F).

Straight grade 5W-30 oils are considered multi-grade because they are suitable for use in colder weather and high-temperature summer conditions.

As viscosity grade numbers are larger, they are also more viscous.

Straight 40 weight oils are lighter and have more fluid than their 30 weight counterparts.

Multi-grade 5W-40 oil is heavier and less fluid than its 20W-50 counterpart.

Oil manufacturers aren’t required to display an oil’s viscosity grade number on the label (they often don’t), but you can find it on the manufacturer’s website or by contacting customer service directly.

Oil Grades – Suitable for All Weathers

Left: 0W; 2; 4; 5; 10; 15; 20; 25; 30; 40; 50

Right: 60

This means that this particular motor oil brand uses a 0W as its base (most common viscosity rating for motor oil, and can be classified in the range of 40 to 60 weight grades, making it a multi-grade 10W-40.

This also means that this particular brand of motor oil is suitable for use in every kind of weather, although not necessarily in all engines or at all times.

For example, an engine designed for heavy-duty use may require a higher viscosity number than one designed for long commutes because prolonged exposure to high temperatures will cause conventional oil to thicken beyond an acceptable limit. Likewise, freezing weather would dramatically reduce the effectiveness of conventional oils.

Winter grade oils are manufactured with additives to resist thickening caused by extreme cold. They usually have lower viscosity ratings than regular oils.

High mileage oil is a type of conventional motor oil that has been specially formulated for high-mileage engines, as the name suggests. High mileage oils contain seal conditioners to help keep seals pliable and eliminate leaks, as well as cleansing agents to remove contaminants from the engine to prevent future sludge build-up, both of which contribute to a longer-lasting engine.

High mileage oil is sometimes referred to as full synthetic, although this isn’t entirely correct because high mileage oils are still fully conventional and not fully synthetic.

Many car manufacturers recommend changing your oil at least every 10,000 miles or ten months, whichever comes first.

At Cutter Mazda of Honolulu, serving Honolulu, HI, we specialize in offering Honolulu residents access to Mazda’s full range of new cars at great prices.

Are you looking for a dealership that takes care of your service? Visit our service & parts specials page to get savings on the maintenance or schedule a service online!

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