What will happen to an engine if I put 15W40 in place of 5W30?

If you put 15W40 oil in place of 5W30 oil in your engine, it is likely that your engine will not run as efficiently. 5W30 oil is designed to flow better in cold temperatures, while 15W40 oil is designed to flow better in warm temperatures.

This means that if you use 15W40 oil in place of 5W30 oil, your engine may not be able to start as easily in cold weather. Additionally, your engine may not run as smoothly or efficiently.

What will happen to an engine if I put 15W40 in place of 5W30?

What will happen to an engine if I put 15W40 in place of 5W30? well Instead of 5w30, if you will use a 15W40, it will result in increasing your engine’s fuel consumption and will have a greater impact on the engine’s crank.

If you put 15W40 oil in your engine instead of 5W30, it’s not the end of the world. The oil will still lubricate your engine and protect it from wear and tear. However, there are a few things to keep in mind.

15W40 oil is thicker than 5W30 oil, so it may not flow as easily through your engine. This can lead to reduced fuel economy and increased engine wear, as the oil may not reach all of the engine’s moving parts.

This in turn will wear out the engine more quickly because the speed of oil movement will eventually slow down.

The thicker oil may also put more strain on your engine’s oil pump, which could lead to failure over time.

If you’re unsure about which oil to use in your engine, consult your owner’s manual or a qualified mechanic.

What are the benefits of using 15W40 motor oil?

15W40 motor oil has a number of benefits. For one, it can help to extend the life of your engine. This oil is designed to protect against wear and tear, which can help to keep your engine running smoothly for longer.

Additionally, 15W40 motor oil can help to improve fuel economy. This oil is designed to reduce friction, which can lead to better fuel efficiency.

Finally, 15W40 motor oil can help to protect your engine in extreme temperatures. This oil is designed to maintain its viscosity in both hot and cold weather, which can help to prevent engine damage.

While there are a number of benefits to using 15W40 motor oil, there are also some downsides. For one, this oil can be more expensive than other types of motor oil. Additionally, this oil may not be suitable for all types of engines.

Before you choose to use 15W40 motor oil, you should do some research to make sure that it is the right oil for your engine. You should also talk to a mechanic to get their opinion on whether this oil is right for your car.

How is 15W40 different from 5W30?

A lot of people for their vehicles prefer using a heavier oil for it to work at a higher RPM. If you put 15W40 in place of 15W30, it might help to sustain for a longer duration.

In most cases, using a heavy oil like 15W40 does not have a noticeable impact and is often recommended for use by manufacturers. However, in certain circumstances, using such oil can result in adverse consequences. 

As newly produced vehicles are manufactured with lesser viscosity, using a high viscosity for some of the components can disrupt the engine and can cause those parts to not function appropriately, impacting the engine’s health and performance.  

When you use a heavy oil like 15W40, the machine can send a trouble code going into a limp mode to run instead of using the start-up time in an effective way.

Will using 15W40 make the head gasket blow off?

To answer this question precisely, NO, using this form of oil for your engine will not have disastrous effects on the head gasket. These components only tend to explode when they are unable to seal anything.

Usually, the head gaskets on most engines seal the chamber combustion pressure, coolant, and oil. In case the oil viscosity is changed, it will not have a major impact on the head gasket.

What will happen to an engine if I put 15W40 in place of 5W30?
What will happen to an engine if I put 15W40 in place of 5W30?

 What is the problem with using 15W40?

When you use 15W40 instead of 1530, it doesn’t give your car proper lubrication as the former is much thicker.

Especially in automated, low mileage automobiles, it will result in producing more noise. For a smoother ride, it is important to follow the car’s recommended oil mentioned in the manual.


Since 15W40 is heavier, it is usually suitable for diesel engines rather than gasoline engines that generally require a lighter fuel. Basically, 15W40 has additives like ZDDP, unlike lighter engine oils.

Usually, 15W30 results in faster wear and tear of the engine because it does not support catalytic converters designed for handling ZDDP. In colder temperatures, thicker viscosity oil is preferred for a smoother operation. 

 How do you choose the right engine oil?

How does one really know which type of oil best meets the needs of their use, especially considering the vast variety of lubricants available in the market?

Is it wise to choose 5W40 or 15W40? Which oil has less viscosity and can readily start engines on a cold morning?

All these questions can sometimes be difficult to answer without appropriate guidance.  In order to choose the right lubricant for your vehicles, it is important to look at the viscosity grades that are recommended or suggested by your OEM (Original Equipment Manufacturer). 

Using the right oil is important as the engine’s life is dependent on the period you use the oil for. The recommendation of the oil depends on not only the ambient temperatures but the expected temperatures that may affect the vehicle and its functioning.

Vehicle’s operating temperature:

The engine has to regulate a certain temperature in order to run smoothly and result in optimal performance. For this reason, it is important to know the viscosity rate for vehicles to start at lower temperatures. 

Apart from temperature control, it is also important to take into consideration the performance level or quality certification of that particular oil.

The quality may vary from level A to level J, representing the lowest to the highest performance levels.

Besides the quality, using a 5W viscosity grade lubricant may result in faster startups and may help with boosting the overall performance of the engine.

People also opt for synthetic lubricants that are readily available in the market with the same level of viscosity or quality. Most of the synthetic oils present currently are approved and recommended by OEM and are well suited for ambient and tropical temperatures. 


How does quality control come into play?

In many countries of the world, including the United States of America, choosing the right engine oil has a lot to do with the kind of quality it has.

The quality ultimately determines the longevity of the engine and the vehicle, making it last for longer and perform at a better rate.

In the US, quality control management for lubricants such as the ones discussed here is done by API (American Petroleum Institute).

All the quality levels ranging from different classes and categories are grouped together and represented by the letter “c”.

A second letter attached to C determines their ability to perform, ranging from the lowest to the highest permanence-based labels.

Can we use a mix of 15W30 and 15W40 for petrol engines?

Ideally, you are not supposed to mix both weights. According to the manual 5W30 does not have a replacement.

If you feel unsure about mixing the varieties, you can always use the manual presented by Bob the Oil guy.

What are the differences in Motor grade oils?

The differences that both the varieties in motor grade have are because of the different properties they own.

A lighter oil like 5W30 provides suitable lubrication for colder regions and reduced fuel consumption because it has less load on the engine’s crank. 


Here are some of the frequently asked questions related to What will happen to an engine if I put 15W40 in place of 5W30?

1. What is the difference between 5W30 and 15W40?

The main difference between the two types of oil for engines is the consistency and thickness level.

The 5W30 is much lighter in comparison. It also represents a cold temperature viscosity because it flows easily in low temperatures.

When an oil like 15W40 gets thick, there are certain additives added to help lubricate the overall flow at lower temperatures. 

2. What do 5W30 AND 15W40 stand for?

The numbers 5 and 15 in the terms represent the level of viscosity whereas the W depicts winterization. The second number, which is 30 or 40 shows whether the oil being used is appropriate for the engine during a particular time and in a specific weather condition.

30 in comparison to 40 is a lot thinner but must be used depending on the markers set by engineers

3. Can 15W40 be used in a warmer climate?

Ideally, you should be using the recommended viscosity oil depending on your vehicle and manufacturing company.

Sometimes it is indicated that a thicker viscosity oil like 15W40 is more suitable for use in warmer climates whereas the alternate thinner versions like the 15W30 are appropriate for colder climates as they remain liquid and don’t clog the engine. Some people even prefer going as low as 10W30 

 4. What are 15W40 oil specifications?

If 15W40 is the right oil for your engine, you must be aware of its specifications. This gas engine is a premium engine oil, specially designed for trucks and buses against the use of CNG (Compressed Natural Gas) or LNG (Liquified Natural Gas). 

The lubrication is formulated to provide a high-quality stock of base and a balanced additive setup. It is highly recommended as it is known for providing excellent nitration, superior oxidation, and thermal stability.

Moreover, it results in less varnishing and carbon building, making it a choice for many. 


One great benefit of 15W40 is its ability to stabilize oxidation and help limit deposits and sludge build-up. Apart from that it significantly reduces oil consumption and offers protection to the cylinder linings.

As a result of its amazing key features, 15W40 yields high speed and output by neutralizing oxyacids.


 Since the lubrication results in lower levels of phosphorus and Zinc, it keeps the engine cleaner and is highly recommended for use.

ExxonMobil suggests that 15W40 is appropriate for CNG and LNG engines as well as dual engines that require 15% of pilot fuel for startups. It is also proven to be useful for heavy vehicles such as trucks and heavy-duty buses. 

Specs and Properties:

The lubrication has a grade of SAE 15W-40, offering Kinematic Viscosity @ 100 C, mm2/s, ASTM D445 at 14.6. It is 0.866 dense and includes around 0.5 of Ash and sulfates. Its total base number is 6. 

Safety and Health:

The Material Safety Data Sheet (MSDS) provides all the specifications of the health and safety features of this lubricant on their website  The trademark is registered by Exxon Mobil Company which comprises multiple subsidiaries 


The new specifications by ILSAC, which have recently been publicized demonstrate that the lubrication industry must be able to meet the fuel economy rules according to EPA standards.

The idea is presented by the fact that when you reduce the viscosity of the oil there is more friction in the motor.

Therefore, using 15W40 might not help the fuel economy, but over the long run, your motor’s life will definitely improve.  



1 thought on “What will happen to an engine if I put 15W40 in place of 5W30?”

  1. Don’t risk your safety to save money on gas. Because 10W-30 is thinner than 15W-40, it has a lower film strength and is more prone to oxidation. As a result, high-quality chemicals are required to compensate for those flaws, allowing 10W-30 to protect as well as 15W-40 and last as long.

    What happens if I replace the 5w30 with 15w40?

    Cold start properties are better with 5w30. Because your engine’s crank is under additional load, using 15w40 instead of 5w30 will raise your fuel usage. It won’t blow off, but it will wear down your engine faster because the oil won’t flow as quickly to the moving parts.

    Simply put, diesel engines emit significantly more soot than their gasoline-burning counterparts. Because of the gap between the piston rings, soot enters the oil pan from the combustion chamber, and it only takes a small amount of soot to convert the oil into the inky black diesel mechanics are all too acquainted with. Diesel engines normally utilize 15w40 oil. Diesel engines normally utilize 15w40 oil. Oil for diesel engines will contain additives that are not required in gasoline engines. However, this isn’t always a terrible thing.


    Metal oil with a higher viscosity seals better than oil with a lower viscosity. Damage to internal engine parts can occur if you use 5W-30 oil instead of 5W-20 when your vehicle’s manufacturer recommends the latter. Additionally, your engine’s performance may be affected, such as reduced fuel economy and horsepower.

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