What Happens If I Use 5w30 Instead Of 5w40 (5w30 Vs 5w40)

Last updated on January 13th, 2023 at 08:38 pm

If you like to know what happens if you use 5w30 instead of 5w40 or maybe you are wondering between the 5w30 vs 5w40 which is thicker,  then this is the article for you. Indeed, the type of car engine oil to use in your car can be found in the owner’s manual. 5w30 and 5w40 engine oils are most commonly recommended by manufacturers. They are the best when you want to start your engine at low temperatures and are very effective in high engine temperatures.  Read this also

This means that you can use them in most weather conditions. However, what are their differences? Today’s article will answer some of your questions such as, what happens if I use 5w30 instead of 5w40? And 5w30 vs. 5w40, which is thicker? After reading, you’ll understand why vehicle manufacturers want you to use one instead of the other in some weather conditions. 5w30 vs 5w40: Which is the Best

In this article I will be discussing the following topics so feel free to skip the part that interest you the most: is it ok to use 5w40 instead of 5w30, is 5w40 good for summer, can I use 5w30 instead of sae 30 in my lawnmower, is there a big difference between 5w30 and 5w40, what happens if i use 5w30 instead of 5w40 and finally I talk a little bit about 5w30 vs 5w40 fuel consumption rate.

Is 5w30 Or 5w40 Better For Summer?

The 5w30 oil is developed to operate a 30 degrees Celsius and it is best used in lower temperatures while the 5w40 is best suitable for use in higher temperatures. The fact that the 5w30 oil operates at 30 degrees Celsius is what makes it the best oil to use in low starting temperatures, and it will also work in high summer conditions. However it is not the idealist, the 5w40 oil is usually recommended for higher engine cars and is ideal for warmer temperatures when compared to the 5w30 oil.

Is It Ok To Use 5w40 Instead Of 5w30?

My answer is yes you can use 5w40 instead of 5w30, but it depends on the temperature range. Note that 5W30 and 5W40 oils are meant to be used during winter or cold temperatures; even at that, both still have thinner quality for the hot temperatures.

Oil such as 5W40 can be used from -40° to 40° temperature capacity, while 5W30 can be used from -30° to 30° temperature range. Do well to examine your owner’s manual, so that you can choose your oil based on the environment temperature, engine type, and fuel economy.

Is 5w40 Good For Summer? (5w30 vs 5w40 which is thicker)

Note that 5W40 is specified for its added thickness and viscosity than 5W30 motor oil. So 5w40 is an oil compatible with both cold and hot temperatures. It is thinner in the summer, and thicker in the winter.

Due to the viscosity of 5W40, it makes sure the overall lubrication of your vehicle components is great for harsh driving conditions. This means you can save extra pennies while using 5W40 as your motor oil since it has good fuel efficiency and less hydrocarbon pollution. This oil is designed to protect your engine and has the following features:

  • 5W40 is compatible with modern, diesel-specified engines, and SUVs vehicles
  • 5W40 has the less or right amount of fuel consumption
  • 5W40 has a fast engine startup and Long engine life
  • 5W40 exceeds the OEM requirements
  • 5W40 works in low, average, and also high temperature

Can I Use 5w30 Instead Of SAE 30 In My Lawnmower?

My answer is yes! There’s a current modified engine oil specification that recommends you to use a synthetic oil like 5W30 in all temperature ranges. 5W30 also has the same flow rate just like SAE30 when in normal operating temperature. 

Is There A Big Difference Between 5w30 And 5w40

Whenever you want to choose a grade of motor oil, you’ll be looking at between performance and protection. Any motor oil that has more viscous while the vehicle engine is running will be fine to protect your engine parts. However, it may be extremely thick to safeguard how your engine performs.

To answer your question, is there a big difference between 5w30 and 5w40? Check their differences below:

For 5w30 oil: 

  • The 5w30 oil has kinematic viscosity which is between 9.3-12.5mm²/s 
  • While its dynamic viscosity is 2.9mPas. 

For 5w40 oil: 

  • The 5w40 oil has kinematic viscosity which is between 12.5-16.3mm²/s 
  • While its dynamic viscosity is 3.5mPas. 

Practically, it shows that each oil is viscous during low temperatures and will have to stay so at -30°C. But 5w40 oil outperforms 5w30 oils during high temperatures, this is due to its effectiveness to ambient temperatures of 50°C, as opposed to 30°C. 

The 5w30 and 5w40 engine oils have winter viscosity grades of five. This simply means that both of them are effective during temperatures of -30°C, and are very viscous during low temperatures. It also means that you can use 5w40 oils in higher-performance engines with a high operating temperature.

5w30 oil is the best option for you if you drive in a more friendly way, or your car isn’t meant to be driven in a high-performance condition. 5w30 oil is best for certain engine parts like oil pumps, as it can clean your engine better, and have increased lifespans since it has a lower temperature range. 

What Happens If I Use 5w30 Instead Of 5w40 ?

This depends on the type of engine you have. Engine oil becomes thinner and will continue being thin the more it gets heated. And when the oil film is broken, metal-to-metal contact will occur, and this will increase the engine’s heat.

Note that there should be no problem as long as the oil pump produces enough pressure to allow the oil to flow into all vital parts. But in case the oil pressure light doesn’t go on while idling, you are likely not causing any damage.

So I advise you to go for 5w30 instead of 5w40. But if 5w30 is too expensive for you, then you can go for 5w40. 

5w30 Vs 5w40 Fuel Consumption

Let’s compare 5w30 and 5w40 based on their fuel consumption.

5W30 is good for modern petrol engines. 5W30 has a lower viscosity and is cost-effective which is great for modern age petrol engines and gives good fuel efficiency. Due to its fuel economy, 5w30 happens to be ranked as the best when looking at performance.

5W40 motor oil is known to be the best for diesel vehicles. 5W40 motor oil performs equally well in higher-performance engines with a high operating temperature.


Both 5W30 and 5W40 motor oils are used in minimizing metal and engine friction and slowly increasing the engine’s lifespan. Even if they both have the opportunity to be used in the summer and winter seasons, they still have their differences. 

Depending on your engine type, I advise you to go for 5w30 instead of 5w40. But if 5w30 is too expensive for you, then you can go for 5w40.  | Difference between 5w30 and 5w40

Sharing is caring!

Scroll to Top