Pick up any bottle of engine oil and you will find it covered with all sorts of labels. Some of them you may already know, some are even more cryptic than a woman, but they are important, nonetheless.

Let us decrypt these details, starting with the SAE grade.

What is an SAE grade?

SAE stands for Society of Automotive Engineers. These are the guys who came up with the standard on oil viscosity grades. As such, you will see this kind of label: SAE 5W-30, SAE 10W-40, SAE 15W-50 and so on.

It has to be said that there are oil brands that do not write "SAE" in front of the grade and just go straight for the numbers. However, you can safely guess that the grade is in accordance to SAE's standards unless you buy some suspicious brand. Still, you can always look for the oil's specification sheet on their website because they are required to publish the specs.

What is viscosity grade?

Viscosity grade represents the viscosity of the oil, or in street talk, thickness of the oil. Scientifically speaking, though, it is the internal resistance of the oil to flow.

An oil with a smaller number is thinner hence easier to flow, while a bigger number means the oil is thicker and slower to flow.

The oil's viscosity is derived from tests at certain temperatures. We will leave the digits with the letter "W" attached for later, so let us look at the second number.

The oil is heated to 100 degrees Celsius and how much flows through into a container is measured against a standard, thus deriving the number. Thus, the more oil is collected means the oil is thinner, hence being given a smaller number; and vice versa.

What about the "W"?

"W" here stands for "Winter." Yes, winter. Not water, not wear, and definitely NOT boiling point (a Tik Tokker once said this). It means what is the oil's winter grade, when everything is frozen over into a winter wonderland.

An oil with a "W" grade means it will remain fluid and not freeze over, therefore allowing the engine to be easily started and circulate the oil.

As such, the "W" rating DOES NOT apply to Malaysia, as the coldest temperature here is 15 degrees Celsius (unless you can ride your bike up to the summit of Gunung Kinabalu). Yes, there are those who said that a smaller number will allow the oil to circulate faster during cold starts but that is not the case, because the "W" rating is attained when tested at 0 degree Celsius.

But why are oils with "W" rating still sold in Malaysia? Because these oils are also sold in other countries around the world, including in countries with winter seasons.

What grade should I use?

The easy and safe answer is to use the grade recommended by your motorcycle's manufacturer. Japanese manufacturers usually recommend lighter grades such as 5W-40 or 10W-40 as their engines' operating temperature is around 65 degrees Celsius. On the other hand, European manufacturers usually recommend thicker oils as their engines run hotter around 85 to 90 degrees Celsius.

However, one can safely use thicker oils as they generally last longer. The trade off is the engine will rev a little slower compared to using a thinner oil.