The 5W-20 and 5W-30 are the most ubiquitous types of motor oil, so they are often used interchangeably. But many motor owners still wonder, is it okay to use the 5W-30 in place of the 5W-20? Above all, is it safe?

The short answer is “Yes.” The 5W-30 oil is not so different from the 5W-20; it is only more viscous. Oils with more viscosity provide more protection against friction and heat, so they do not thin out easily. Hence, the 5W-30 relatively protects your engine better than the 5W-20.

It is crucial to note that if your vehicle type and model requires the 5W-20 motor oil and you switch to 5W-30, you may notice a change in your engine’s efficiency and fuel economy. Both oils have the same viscosity in cold conditions, but the 5W-30 oil has a slightly higher viscosity at 100°C.

What this means is that the 5W-30 is thicker in normal operating conditions, which also means it will provide better protection in normal operating temperatures.

We’d recommend not switching your oil type from the manufacturer’s recommended engine oil type if your vehicle is still under warranty. If you use a different one from the recommended oil type in the car owner’s manual, you risk voiding the warranty should a problem develop in the powertrain. Now, let’s take a quick look at the essentials you need to know about oil viscosity and its various types.

What Is Oil Viscosity?

Oil viscosity is the resistance to flow the oil possesses at various temperatures. It refers to the measure or speed at which oil flows or travels at different temperatures. Oil ratings like 5W-20 or 5W-30 are there to tell you what the viscosity of the oil is. If the oil has a higher rating, it implies that it is thicker and doesn’t flow as fast as the ones with a lower rating.

High-viscosity oils (oil types that are thicker and flow with less speed) are thus better suited to engines that run hot or if you drive in hot temperatures. Low-viscosity oils, on the other hand, are perfect for cold temperatures because they are thinner and have less resistance to flow.

The 5W-20 and 5W-30 are known as multi-grade oils because they can have two different ratings depending on the external temperature. For example, the 5W-20 oil has two viscosity rating numbers. This is because multi-grade oils have polymers that increase in size as temperature rises.

Let’s try a bit of math for a clearer understanding. The first number in the sequence, which is 5, indicates the winter rating of the oil (the oil viscosity when the temperature is 40°C). While the second number, which is 20 in this example, shows oil viscosity at 100°C. You call this math? I know, right?

5W-20 vs. 5W-30

As explained above, since both oil types have the same winter rating, their viscosities in colder temperatures are the same. So, it’s safe to use any of them for your engine if you live in Antarctica or Russia, or Greenland. The ‘W’ in the ratings is actually short for “winter,” making it easy for you to pick out what you need.

The most significant difference between these two ratings is how they behave in high temperatures. The 5W-30 is more viscous at a higher temperature, so it won’t thin out to the point where its purpose is defeated as the engine reaches its operating temperature.

 To Recap

• You can use both the 5W-20 and 5W-30 oils for your vehicle if your engine doesn’t get too hot and you don’t typically drive in hot weather conditions.
• The 5W-30 is preferable for scorching weather, while the 5W-20 is better suited for cold temperatures.
• Read your instruction manual to know more about your vehicle’s oil type, and do not switch oils if your vehicle is still under warranty.