Skip to Content

What Happens If You Use 10w40 Instead Of 5w30? [ Know Here ]

What Happens If You Use 10w40 Instead Of 5w30? [ Know Here ]

You might notice automobile manufacturers often recommend using a specific oil for their cars or trucks. This same principle applies when it comes to choosing the fluid for your power steering or any fluid as such.

As an automobile owner, you might feel tempted to use any other non-recommended fluid, considering aspects like availability and price. Particularly, you might be confused over whether to use 5w30 graded motor oil, or 10w40.

Before recommending the engine oils for your car, the manufacturers examine the results of testing these fluids in labs. Some of these oils also come with additives.

Many car owners interchange these motor oils. In this article we have discussed whether you can replace one oil with the other in your car.

Can I use 10w40 instead of 5w30?

You can use 10w40 motor oil rather than 5w30 motor oil only under emergent conditions. However, experts recommend not to do so. Replacing one engine oil with another wouldn’t bring about any substantial enhancement in the performance of your car.

Neither would it enhance its lifeline in any way. The level of viscosity in these two motor oils is different. They are suitable for vehicles operating with different temperatures.

Therefore, replacing the engine oils wouldn’t be a practical decision for car owners. As you know, the viscosity of motor oil goes a long way in influencing your vehicle’s performance.

Also, replacing the engine oil might cause different problems in your car.

What happens if you use 10w40 instead of 5w30?

In case you decide to replace the 5W30 with 10W40 oil, your car might face several hazards. 10W40 oil is relatively thicker than the other one.

Therefore, if your car’s engine needs a thinner fluid, it would affect its performance. Although experts recommend slightly interchanging the engine oils sometimes, you cannot replace them altogether.

  • 5W30 engine oil is suitable for operations in colder temperatures. The oil is thinner, which enables it to flow freely at a colder temperature. Particularly, it prevents the jamming of oil inside the vehicle’s mechanical components. Therefore, if you opt for a thicker fluid, your car’s engine would fail to deliver the desired performance quality.
  • Moreover, you might encounter clogging issues that would rob the car of its functional efficiency.
  • Besides, when you use a thicker oil, it would fail to make its way to all the engine components when you start it. Eventually, your car would experience a lack of lubrication, leading to friction and wear.
  • The car needs more oil flow in its cooling nozzles and piston. When you apply 10w40 oil to these places, the flow speed would decrease as this oil is thicker. This would result in inadequate cooling of the engine parts. So, automobile manufacturers recommend using thinner fluids for these purposes.
  • The rods and bearings of your car undergo wear and tear continually due to abrasion. Therefore, these parts need thicker oil for better protection. You cannot replace a thicker oil with a thinner one for these parts.

Is 10w40 better than 5w30?

The two types of engine oils serve two different purposes. While one is thinner, the other is more viscous. Naturally, you have separate applications for these two types of engine oils.

For hotter regions, you need a high viscosity oil like the 10W40. On the other hand, you need a low viscosity oil like the 5W30 or colder regions. So, you cannot directly compare these two engine oils. Each one of them is ideal for its respective purpose.

10W40 vs. 5W30: Know all the details

10W40 engine oil5W30 engine oil
Viscosity is highViscosity is low
SAE certifiedSAE certified 
Very good lubricationVery good lubrication
Not recommended for engines that frequently idleRecommended for engines that frequently idle
Ideal for older carsIdeal for newer cars
Works well in high-temperature regionsWorks well in cold temperature regions
The oil is more viscousIt is thinner than 10w40 oil

10w40 Motor Oil

10w40 is a synthetic motor oil. When the engine is warm and the temperature is high, it has a viscosity level of 40. At a lower temperature, when the engine is normal, the viscosity level comes to around 10.

So, you need 10w40 motor oil for higher temperatures, as the viscosity level would be pretty low when it works in high temperatures.

5w10 Motor Oil

5w30 is among the common synthetic motor oils. However, this oil is not as viscous as the 10w40 oil. The nomenclature and number show that the viscosity rating of this oil at a low temperature is just 5.

So, the thickness level of this oil would only be half of the 10w40 oil. However, this level of viscosity rises to 30 when the temperature is high. This is also lower than that of 10w40.

What is the difference between 10W40 and 5W30 engine oils?

In general, 10W40 engine oil is thicker than 5W30 engine oil. So, when the temperatures are cooler, you need to use 5w10 oil for your engine. On the other hand, when you drive in warmer conditions, you need to use a high-viscosity engine oil like the 10w40.

Since 5w10 has a low viscosity, it functions better when the temperatures are low. It would also secure various parts of your car’s engine in low temperatures. It would be a more practical option for your vehicle when the internal heat of the engine remains relatively low.

Thanks to the higher viscosity of 10w40 engine oil, it would secure the engine parts better. When you drive the car constantly at high speed, you would need this type of engine oil.

However, you need to be strategic when choosing the right engine oil. For example, driving in low-temperature conditions doesn’t always require you to use 5w30 oil.

Likewise, driving through tropical zones, you wouldn’t need 10w40 oil every occasion. You simply need to adhere to the recommendation of the manufacturer. They understand your car better than you do, so it would be wise to follow their instructions.

Thickness or viscosity

Viscosity measures the level of thinness or thickness of any fluid. In the case of car oil, viscosity refers to its density. You need to consider both the numbers in each engine oil grade while determining its viscosity.

The lower the numbers, as you can see in the case of these two oils, the thinner it would be. This explains why 10W40 is thicker than 5W30 oil.

Gas mileage

When considering your car’s mileage, you need to prioritize the thickness of the oil. Viscous oils habitually deliver better mileages. In our discussion, we have considered 10W40 and 5W30 oils.

Since the former has a greater viscosity, it would deliver better mileage. In this context, you must note that 5W30 oils do not deliver in poor mileage for your vehicles.

It works perfectly fine for vehicles for which the manufacturers recommend the specific oil. Driving in colder temperatures is challenging. Under these circumstances, they deliver the best mileage.

Evidently, it would be wise to use 10w40 and 5w30 oils only for the recommended vehicles that accept them. Otherwise, it might prove adverse for your car’s engine and overall functionalism.


Simply follow the manufacturer’s recommendation, as they design the engines specifically for your vehicle. Each engine has its own requirement, and this explains why you should use the recommended oil. It would suit your engine better than any other fluid.

As a thumb rule, you need to use 10W40 oil when you drive in warmer environmental conditions and 5W40 in colder places.

Also, you should use 5W40 engine oil in case you use your car less frequently and the engine sits idle often. This would also prevent the oil in the engine from developing lumps and freezing.