Motorcycle engine oil - What do the letters and numbers mean?

There is always some sort of confusion among motorcycle riders as to what engine oil to use. Whether it’s what brand to use or how frequently you should change it. But what really gets confusing is the numbers written on the engine oil boxes. What do they mean? And what’s their significance? Let’s find out.

Every box or packet of motorcycle engine oil will have its grade specified on the front of the packaging. It will be denoted by a number separated with a ‘W’ for e.g. 20W40 or 10W40. The letter ‘W’ stands for winter and the number preceding the W is the low temperature limit while the number following the W is the hotter temperature limit. These numbers are important because different motorcycle engines function under different temperatures and your engine oil should be able to handle these temperatures. For the engine oil to perform well, it has to hold on to a certain viscosity level for optimum performance. For example, when you start your motorcycles engine for the first time in the morning, the engines parts as well as engine oil are cold. As soon as the engine starts up, the oil needs to be circulated as early as possible to provide maximum protection from wear and tear. In this kind of situation the engine oil's property should be thin enough to circulate at the earliest. If the engine oil is too thick, then it would take some time to reach across the various engine parts. So the lower the low temperature count, the better will be the cold start performance for the engine.

When it comes to the higher temperature limit, remember that the engines temperature can reach over 100 degrees Celsius, and engine oils tend to lose their viscosity and get thinner if the temperatures go beyond their specified rating. This is why most manufacturers recommend a certain grade of oil for the smooth functioning of the engine depending on the performance of the engine.
So if you have a motorcycle whose engine tends to runs into higher temperatures easily, then a low rating of high temperature grade will make the oil thinner and cause engine damage due to high friction over time. So for bigger high performance motorcycles, a higher grade oil is preferred so that the oil holds its viscosity even at higher temperatures.

Now you know what the numbers on the engine oil box mean. But, it is always better to stick to the engine oil recommended by the motorcycle manufacturer. You can find the engine oil grade specified by the manufacturer in your owner’s manual. You can always change the brand of engine oil and if you know you’re going to be using the motorcycle for sport use or on the track, you can experiment with a higher grade of engine oil. For regular use, we suggest you stick to what the manufacturer has recommended.