10w40 vs 20w50 engine oil. Differences and characteristics

Car engines have not been designed to work on oil of one type only because they require a change over time based on the age of the engine.

The manufacturers match and mix different oils for different types of engines to ensure an engine has the best lubricant oil. There is hence no one-size-fits-all oil formula that works in all situations for all cars.

Different types of oils are available in the market depending on their functionality and specifications, such as thickness, viscosity, the weight of the oil, and others.

Here, we will look at 10w40 vs. 20w50 oil, the two most popular oil types, so you can understand the best type of oil to use.

While both 10W40 and 20W50 are ideal for winter and summer temperatures, they are not the same. The major difference between the engine oils is their viscosity index. 10W40 has a viscosity index of 150, whereas, for 20W50, oil is 130. The higher the viscosity index, the better the engine oil output.

What Is 10w40 Engine Oil and What Engines Can It Be Used For?

10W40 is one of the popular engine oils most recommended for modern-day engines or vehicles. Additionally, all vehicles above 2012 have modern engines that need more lubrication and cold temperature pumping.

Therefore, 10W40 oil is considered a suitable pick for fast vehicles or cars in cold climates rather than heavy-duty engines. Also, 10w40 oil is recommended for engines that have passed the 100000 km or 60000 miles to better lubricate the engine.

The numbers on the name indicate the viscosity of 10W40. The number 10 shows the oil’s viscosity rating at low temperatures, -25 degrees Celsius or -13 degrees Fahrenheit while 40 indicates the oil viscosity rating at operating or high temperatures, +40 degrees Celsius or +104 degrees Fahrenheit

10W40 oil offers better flow to engine components and protects the piston skirts and bearings when generating heat. If you have a high-performance engine and modern vehicle that requires extreme lubrication and protection, 10W40 is a perfect pick. 

What Is 20W50 Engine Oil and What Engines Can It Be Used For?

20W50 is another manufacturer-specified engine oil. This means that you should only use the oil when recommended by the manufacturer’s manual.

The 20W50 is mostly preferable for cars with the efficiency of operating at high temperatures. This oil is also primarily ideal for summer cars as well as vehicles operating in a mild winter season. It has a kinematic viscosity of 16.3 – 21.8 mm²/s.

If you drive your car for a long time at high speed, the engine begins to heat up. This heat causes serious tears and wears if the engine components do not receive sufficient lubrication. In this situation, 20w50 is a great option to cope with that stress.

More so, if you are staying in a cold region where your car stays in the garage idle for more than a week, it requires a cold start. 20W50 gives the ideal lubrication to get a cold pumping in the engine proficiently.

The viscosity of 20W50 oil is what makes it ideal for both winter and summer vehicles. The numbers on its name specify the viscosity at low and high temperatures.

Number 20 and w represent the viscosity of the oil at winter or low temperatures, operating at a minimum of -20 degrees Celsius or -4 degrees Fahrenheit.

The number 50 shows the viscosity of the oil at operating or high temperatures, operating at a maximum of +45 degrees Celsius or 113 degrees Fahrenheit.

If your car is a pick-up truck or highway fleet, it normally runs more than passenger cars. This means you will need to change your vehicle oil more often.

20W50 oil is the best budget option for heavy and old vehicle engines to provide them with long life and proper lubrication.

10W40 and 20W50 Oil Differences

1. Viscosity

10W40 oil has a 40th viscosity grade, while 20W50 has a 50th viscosity grade. This means 10W40 is more viscous than 20W50 at low temperatures making it best for winter vehicles.

On the other hand, 20W50 is best for use in hotter climates. Keep in mind to stick to the prescribed viscosity grade by the manufacturer.

2. Density

10W40 has a lower density of 865 kg/m3 than the denser 20W50 at 872 kg/m3. As far as the mileage is concerned, there will be no increased mileage by using either 10W40 or 20W50.

3. Additives

Both 10W40 and 20W50 are produced from high-quality base oil blended with additives to meet their unique characteristics. This gives both oils good thermal stability and oxidation.

4. Operating temperature

10W40 oil has a low-temperature viscosity of -25 °C or -14 °F, while 20W50 is -20 °C or -4 °F. The high-temperature viscosity for 10W40 is 40 (40 °C or 113 °F) while that of 20W50 oil is 50 (+45 °C or +113 °F).

This makes 10W40 oil suitable for cold climates and the latter for hotter climates.

5. Price

When it comes to price, 10W40 oil is more expensive when compared to 20W50. Therefore, if your car is a highway fleet that needs regular oil replacement, 20W50 is an ideal budgeted oil, cheaper than the 10W40. 10w40 is costly and ideal for light vans or passenger cars without changing the oil frequently.

Can I use 10W40 instead of 20w50?

From what we have discussed above, the type of oil you should use depends on the season, the type of vehicle, how fast you drive, etc. If you use 10W40 oil in a vehicle that needs 20W50 for an extended period, oil can damage the engine.

Some mechanics may recommend using 20W50 or 10W40 as part of regular service schedules regardless of the type of car you drive.

You should always follow the instructions of your owner’s manual to see what oil suits best your engine and your mechanic recommendations because they have more experience with cars and engine issues.

Is 10W40 the same as 20w50?

No, both engine oil types are very different. While 10w40 is more often used. 20w50 can be used under some circumstances.

What happens if I put the wrong oil in the engine?

Using the wrong oil in the engine can result in significant damage to your engine. The car will start losing its strength and won’t lubricate as intended. Different oils have unique flow characteristics and different viscosities.

Using the wrong oil can hence cause leakages and noisy engines. Additionally, putting the wrong engine oil with a lower winter or cold viscosity than what the manufacturer recommends can cause the car not to start in cold weather.

However, if you do a good and regular oil change with either 10W40 or 20W50, you should not experience any issues with sludging.


Each oil has its unique differences and qualities. Therefore, it is essential to use the right type of oil for your vehicle engine to help it run smoother and avoid engine failures.

Refer to your vehicle manufacturer’s manual to see the ideal oil types for your car, such as regular oils or synthetic oils. If 10W40 and 20W50 are compatible with your car, consider the differences and similarities to choose the best one among the two oils.

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