5w20 vs 5w30 – You need to know the difference

One of the most vital car care tasks involves changing engine oil once in a while depending on the mileage covered. The 5W20 and 5W30 oils are the most common motor oil options which exhibit impressive performance under hot or cold temperature conditions. Even while both engine oils work under a range of possible temperatures, their difference is crystal-clear. In this article, we focus on the 5W20 vs. 5W30 engine oils.

5w20 vs 5w30

5W20 vs. 5W30 – Viscosity

The main difference between the 5W20 and 5W30 engine oils is viscosity. Viscosity determines the resistance of the motor oil to flow under a given temperature, or simply the thickness of oil when subjected to heat. The letter “W” assigned before the number indicates “winter” or low temperatures the oil can withstand.

Oil models with a higher number are thicker (less viscous) and more difficult to get thin under the influence of heat. On the other hand, oil models with a lower number are thinner (more viscous) and can easily break down under higher temperatures. In this case, the 5W30 engine oil has a higher viscosity while the 5W20 engine oil has a lower viscosity.


When the 5W20 oil is used in a vehicle’s engine, its thinner viscosity creates less friction or drag across the engine parts like pistons, valve-train and crankshaft. In so doing, it provides a slight bump in fuel efficiency. The thinner oil like the 5W20 is recommended for use under very cold temperatures because it can flow easily from the oil pan to the other parts of the engine on start-up.  

On the contrary, the thicker 5W30 engine oil plays a significant role in hotter temperatures where thinner oils tend to easily break down when subjected to higher temperatures. Engine oils which never break down under higher temperatures provide better overall protection to the internal parts of the vehicle engine. For the most part, both oils equally protect your engine irrespective of the climatic condition or season, but the 5W30 provides more protection under higher temperatures while the 5W20 provides better protection under lower temperatures.

 5W20 or 5W30 – Which one is more economical?

The 5W20 engine oil has a lower viscosity and provides a thinner layer of protection when the vehicle is running at normal operating temperature. With less oil laced between the moving parts of the engine, the 5W20 provides less friction, which translates to better performance. Using a lower viscosity oil not only improves the performance but also heightens fuel efficiency and gas mileage.


However, even though a lower viscous oil flows easily to hard-to-reach spots to provide less friction for the engine components and inspire performance, fuel efficiency comes at a cost. Given its texture, the less viscous 5W20 engine oil will eventually become too thin to minimize friction when the temperature spikes up. Therefore, despite an improved fuel economy, there will be an unusual jump in your MPG in the long term.

So, whereas the less viscous 5w20 oil is an excellent choice at normal temperatures, it might become too thin under hotter temperatures. Sure, your gas mileage will improve big time when it gets thin enough to flow into difficult parts of the engine. However, it might reach a point where it will compromise on the lubrication of the engine causing excessive wear and tear.

Final Thought:

The 5W20 and 5W30 engine oils have been the subject of discussion for quite a long time. Car owners often find themselves confused on whether to choose the 5W20 or 5W30 for their engines. The key to choosing either of these oils lies in understanding their advantages and limitations relative to your vehicle engine’s requirements.

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