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Engine Oil – What do Markings on Tell Us?

Engine Oil – What do Markings on Tell Us?

  • Every bottle of engine oil is covered with markings.
  • These markings contain important information.
  • What do these data mean?

It goes without saying that choosing the correct engine oil is critical in protecting the engine, besides unlocking its performance.

But engine oils are rather specific these days and choosing the right one can be a daunting venture. However, fear not as each bottle (or whatever container they come in) is covered with information. It is this information that tells us if the oil is suitable for our bike.

So, let us get down to the basics.

Types of Engine Oil

There are three types of engine lubricants, namely:

  • Mineral.
  • Semi-synthetic.
  • Fully-synthetic.

All engine lubricants obtain their base oil from various sources. It is this base oil and its composition which determines if the end product is mineral, semi-synthetic, or fully-synthetic.   A pure base oil cannot be used directly in the engine. Instead, it is mixed with different additives (called “additive packages”) to produce the desired attributes such as protection characteristics, viscosity stability, wear characteristics, and many more.

  • mineral engine oil means it uses a base refined from raw petroleum. It generally has the least protection and performance attributes, besides breaking down quickly. It is therefore the cheapest.
  • Semi-synthetic means the product has a mix of mineral and synthetic base oils, with no more than 30% of the latter. This lasts longer and provides better performance than mineral engine oil. It is priced in between mineral and fully-synthetic oils.
  • A fully-synthetic engine oil uses a base that’s wholly produced in a laboratory rather being dug from the ground (except for gas-to-liquid base oil). The advantage here is that the base can be tuned for a certain attribute from the outset even before mixing in additives. This is why fully-synthetic oils are the most expensive among the three.
Viscosity Index (VI)

The oil’s VI is specified in terms such as these: SAE 5W-40, SAE 10W-40, SAE 15W-40, SAE 15W-40 and so forth. These grades are specified by the SAE (Society of Automotive Engineers). These are called “multigrades” because they have different VIs at different temperatures.

An oil’s viscosity – usually called as “thickness” – is another, if not the most, important factor in choosing the right oil. A fluid with lower viscosity (lower VI value) flows easier and we usually call it “thin.” Conversely, a more viscous fluid (higher VI value) flows slower and we call it “thick.”

Hence, a 15W-50 oil has higher viscosity than a 10W-40 oil, at the same temperatures.


What do the numbers tell us?

The letter “W” means “winter” and the number in front of it refers to the oil’s viscosity at 0-deg Celsius. In other words, a 5W-40 oil maintains a viscosity index of 5 at 0-deg Celsius. As such, the oil does not freeze solid in winter and allows it to be pumped around the engine during cold starts.

Consequently, the W-rating does not apply to us living in the tropics as we do not see 0-deg C temperatures. It does not apply to the highlands either.

The second number indicates the oil’s viscosity at working temperatures. Although oils thin as temperature increases, it must withstand that heat and maintain a certain viscosity. Otherwise, the oil becomes too thin to protect the engine’s moving parts. The number tells us the viscosity of the oil at 100-deg C.

Please refer to the graph above. Most motorcycle manufacturers specify 10W-40 or 15W-40 grade oils (depending on type) for our country. Some riders prefer the XXW-50 fully-synthetic oils as they last longer and also provide better sealing in older engines.

DO NOT use engine oils that are too thin or too thick. Too thin may not provide adequate protection, while too thick means the oil may not seep into the small gaps between moving parts.

First of all, these letters refer to “service grades” set by the American Petroleum Institute’s (API) classifications, hence they DO NOT indicate the oil’s quality or viscosity.

Instead, the service grades refer to the oil’s compatibility to an engine’s performance. In that sense, newer vehicles need lubricants of higher classification.

API works closely with vehicle manufacturers to specify an oil’s properties in relation to soot thickening, seal compatibility, after-treatment compatibility, fuel economy, oxidative thickening, piston deposits, sludge and wear to assign the classification to the oil.

The current standard for petrol engines is SP which took effect on 1st May 2020. However, most lubricant producers have not made products for that classification as of March 2021. Thus, the SN grade, which was introduced in October 2010 for vehicles produced from 2011 onwards, still applies. Grades SA through SH are considered obsolete and should not be used.

So, what if you find oils with SL or SM grades? You can still use them but the SN grade oil should have better properties.



This is what makes a motorcycle-specific engine oil critically different from an engine oil for cars.

A car engine does not share its engine lubricant with its clutch and gearbox, while a motorcycle does – hence the term “wet clutch.” Using a car engine lubricant in a motorcycle engine with wet clutch will cause the clutch’s pressure and friction plates to slip against each other. Also, a motorcycle’s engine oil must stand up to the shearing forces exacted by the gears in the transmission, while a car’s oil is not designed for it.

An engine oil which complies with JASO MA or JASO MA2 standards means it can be used in engines with wet clutches. The standard is JASO T 903:2006. However, the oil must be of API SG classification and above in order to meet the standard.

You may use a JASO MA or JASO MA2 certified lubricant for a scooter, but not a JASO MB (for scooters) in a bike with a wet clutch.



So there you go. We hope you keep these information in mind for your next oil change. If in doubt, refer to the motorcycle’s User Manual.

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