5W-30 vs 5W-40 Engine Oil: Which One Is Right for Your Car?

Sep 24, 2026

Rahul Gupta

5W-30 vs 5W-40 Engine Oil: Which One Is Right for Your Car?

Choosing the right engine oil is an important part of maintaining your car's engine. With different viscosity grades available, one common question among car owners is: 5W-30 vs 5W-40 — which engine oil is right for my car?

Both 5W-30 and 5W-40 are multigrade engine oils designed to provide lubrication across different operating temperatures. However, they have different viscosity characteristics at higher operating temperatures.

The important thing to remember is that there is no universally better choice between 5W-30 and 5W-40. The correct engine oil depends on your vehicle manufacturer's recommended viscosity, required performance specification, engine design and operating requirements.

In this guide, we'll explain the difference between 5W-30 and 5W-40, their applications, fuel-economy considerations, turbocharged engines, petrol and diesel cars, and how to select the right engine oil for your vehicle.

5W-30 vs 5W-40: Quick Difference

The easiest way to understand the difference is to look at the numbers.

Feature	5W-30	5W-40
Low-temperature grade	5W	5W
High-temperature grade	30	40
Operating-temperature viscosity	Lower	Higher
General characteristic	Lower viscosity at operating temperature	Higher viscosity at operating temperature
Selection	Follow vehicle manufacturer's recommendation	Follow vehicle manufacturer's recommendation

Both oils have the same 5W winter viscosity grade. The primary difference is the second number: 30 vs 40.

This means 5W-40 has a higher viscosity grade at operating temperature than 5W-30.

What Does 5W-30 Mean?

5W-30 is a multigrade engine oil viscosity grade.

The 5W indicates its low-temperature viscosity classification, while 30 represents its high-temperature viscosity grade.

The "W" stands for winter, not "weight."

A 5W-30 engine oil is therefore formulated to maintain suitable flow characteristics at lower temperatures while providing the viscosity characteristics required at normal engine operating temperatures.

However, the SAE viscosity grade alone does not describe the complete performance of an engine oil. The oil should also meet the performance specification required by the vehicle manufacturer.

What Does 5W-40 Mean?

5W-40 is another multigrade engine oil grade.

Like 5W-30, it carries a 5W low-temperature classification. Its difference is the 40 high-temperature viscosity grade.

At operating temperature, 5W-40 has a higher viscosity grade than 5W-30.

This makes 5W-40 appropriate for engines where the manufacturer specifies or permits this viscosity grade.

A higher viscosity grade should not automatically be considered better. Engine manufacturers design lubrication systems around specific viscosity and performance requirements.

Is 5W-40 Thicker Than 5W-30?

Yes.

At operating temperature, 5W-40 has a higher viscosity grade than 5W-30.

In simple terms:

5W-30 → Lower operating-temperature viscosity

5W-40 → Higher operating-temperature viscosity

But "thicker" does not mean "better for every engine."

Modern engines are designed with specific oil-flow requirements, clearances, lubrication passages and performance targets. Using an oil that does not match the manufacturer's recommendation can affect how the lubrication system is intended to operate.

Therefore, always check the owner's manual before changing viscosity grades.

5W-30 vs 5W-40: Which Is Better for Your Car?

The answer depends on what your vehicle manufacturer recommends.

If your owner's manual specifies 5W-30, use an appropriate 5W-30 engine oil that also meets the required performance specification.

If your owner's manual specifies 5W-40, choose a suitable 5W-40 engine oil meeting the required specification.

Some vehicles may permit more than one viscosity grade depending on operating conditions. In such cases, follow the manufacturer's specified recommendations.

The important rule is:

Choose the engine oil recommended for your specific engine rather than choosing an oil simply because it is thinner or thicker.

5W-30 vs 5W-40 for Petrol Cars

Both 5W-30 and 5W-40 can be used in petrol-engine applications where specified by the vehicle manufacturer.

Modern petrol engines can have different lubrication requirements depending on:

Engine design
Turbocharging
Emission-control technology
Fuel-economy requirements
Engine operating temperature
Manufacturer specifications

For example, a modern turbocharged petrol engine may require a specific viscosity and performance category designed to support the engine's operating requirements.

Therefore, when selecting engine oil for a petrol car, check both:

SAE viscosity + required performance specification

Do not select the oil based only on the 5W-30 or 5W-40 label.

5W-30 vs 5W-40 for Diesel Cars

Diesel engines can have different lubrication requirements from petrol engines.

The correct oil may depend on engine generation, emissions technology, turbocharging, after-treatment systems and manufacturer specifications.

For modern diesel vehicles, especially vehicles equipped with advanced emission-control systems, using the correct oil specification is particularly important.

If your vehicle manufacturer specifies 5W-30, use the appropriate 5W-30 product.

If it specifies 5W-40, use the appropriate 5W-40 product.

Always check the owner's manual for the exact requirement.

5W-30 vs 5W-40 for Turbocharged Engines

Turbocharged engines operate under demanding conditions, with the turbocharger exposed to high temperatures and speeds.

However, turbocharging alone does not mean that 5W-40 should always be used.

Some turbocharged engines are specifically designed for 5W-30, while others may require 5W-40 or another viscosity grade.

When selecting oil for a turbocharged engine, consider:

Recommended SAE viscosity
API/ACEA specification
OEM requirements
Engine type
Emission system
Manufacturer-approved oil

The correct specification matters more than simply choosing a higher viscosity.

Does 5W-30 Improve Fuel Economy?

One reason modern vehicles may use lower-viscosity engine oils is to help meet fuel-efficiency requirements.

Under appropriate conditions, lower-viscosity oils can reduce fluid friction. However, this does not mean switching from 5W-40 to 5W-30 will automatically increase your vehicle's mileage.

Actual fuel economy depends on many factors, including:

Driving habits
Traffic conditions
Vehicle weight
Tyre pressure
Engine condition
Fuel quality
Vehicle design
Maintenance
Engine oil specification

If your vehicle manufacturer recommends 5W-30, using the correct 5W-30 oil can help maintain the lubrication characteristics intended for that engine.

Does 5W-40 Provide Better Engine Protection?

It would be incorrect to say that 5W-40 automatically provides better engine protection simply because its operating-temperature viscosity grade is higher.

Engine protection depends on the complete formulation and performance specification of the oil, as well as whether it is suitable for the particular engine.

An oil with the wrong viscosity or performance specification may not be appropriate even if it appears to be a "thicker" or more protective option.

Therefore:

Higher viscosity ≠ automatically better protection

The correct oil is the oil that meets the engine manufacturer's requirements.

Can You Use 5W-30 Instead of 5W-40?

Not automatically.

If your vehicle's manufacturer specifies 5W-40, do not switch to 5W-30 simply because it may have lower viscosity at operating temperature.

Check whether the manufacturer explicitly allows both grades.

If multiple grades are listed in the owner's manual, follow the specified operating conditions and recommendations.

Can You Use 5W-40 Instead of 5W-30?

The same principle applies in the opposite direction.

If your vehicle manufacturer recommends 5W-30, do not automatically replace it with 5W-40.

A different viscosity may affect the engine's intended oil-flow and lubrication characteristics.

Always refer to the vehicle manufacturer's recommended SAE grade and performance specification.

5W-30 vs 5W-40 in Hot Indian Weather

India experiences a wide range of temperatures and driving conditions.

It is common for car owners to think that hotter weather automatically means they should use a thicker engine oil.

However, ambient temperature alone should not determine whether you use 5W-30 or 5W-40.

Vehicle manufacturers consider engine design, lubrication requirements and operating conditions when specifying oil grades.

So even if you live in a hot city, do not change your engine oil viscosity without checking the manufacturer's recommendation.

Why Is the API Specification Important?

SAE viscosity tells you about the oil's viscosity classification.

The API performance category, where applicable, provides additional information about the oil's performance level and intended engine application.

For example, modern gasoline engine oil categories can include requirements relating to areas such as:

Deposit control
Timing-chain wear
Turbocharger protection
Low-speed pre-ignition protection

Therefore, choosing an engine oil involves more than simply selecting 5W-30 or 5W-40.

You should check:

SAE Grade + API/ACEA Specification + OEM Requirement

5W-30 vs 5W-40: What Should You Check Before Buying?

Before purchasing engine oil, check these five points:

1. SAE Viscosity

Check whether your vehicle requires 5W-30, 5W-40 or another viscosity grade.

2. API Specification

Check the required API performance category specified for your vehicle.

3. ACEA Specification

For vehicles requiring an ACEA specification, make sure the oil meets the appropriate requirement.

4. OEM Requirement

Some vehicles require specific manufacturer approvals or specifications.

5. Vehicle Owner's Manual

The owner's manual remains one of the most reliable sources for determining the recommended engine oil.

Bharat Lubricants 5W-30 Engine Oil

For vehicles that specifically require SAE 5W-30, Bharat Lubricants offers:

BHARAT Semi Synth MGEO 5W-30 SST

View BHARAT Semi Synth MGEO 5W-30 SST

Before purchasing, always confirm that the product's viscosity and performance specifications match your vehicle manufacturer's requirements.

Bharat Lubricants 5W-40 Engine Oil

For vehicles that specifically require SAE 5W-40, Bharat Lubricants offers:

BHARAT Semi Synth MGEO 5W-40 SST

View BHARAT Semi Synth MGEO 5W-40 SST

As with any engine oil, check the vehicle manufacturer's recommended viscosity and required performance specification before selecting the product.

5W-30 vs 5W-40: Bharat Lubricants Comparison

Requirement	Recommended Bharat Product
Vehicle requires SAE 5W-30	BHARAT Semi Synth MGEO 5W-30 SST
Vehicle requires SAE 5W-40	BHARAT Semi Synth MGEO 5W-40 SST
Unsure about viscosity	Check vehicle owner's manual
Specific API/OEM requirement	Verify product specification before purchase

Important: The product should be selected based on the vehicle manufacturer's requirements, not simply on preference for 5W-30 or 5W-40.

Common Mistakes When Choosing Engine Oil

Choosing Only by Viscosity

Seeing "5W-30" or "5W-40" on the bottle is not enough. Always consider the complete specification.

Assuming Thicker Oil Is Better

5W-40 has a higher operating-temperature viscosity grade, but that does not mean it is automatically better for every engine.

Changing Oil Because of Weather

Hot weather alone is not a sufficient reason to change from 5W-30 to 5W-40.

Copying Another Car's Oil Grade

Two vehicles with similar engine capacities can have different oil requirements.

Ignoring the Owner's Manual

The owner's manual should be the starting point when selecting engine oil.

5W-30 vs 5W-40: Frequently Asked Questions

Is 5W-40 thicker than 5W-30?

Yes. At operating temperature, 5W-40 has a higher SAE viscosity grade than 5W-30.

Which is better, 5W-30 or 5W-40?

Neither is universally better. The correct choice depends on the engine manufacturer's recommended viscosity and performance specification.

Can I mix 5W-30 and 5W-40?

It is generally better to avoid mixing different viscosity grades unless necessary. Follow the vehicle manufacturer's recommendations and use the specified engine oil.

Is 5W-30 good for petrol cars?

It can be suitable for petrol cars when the manufacturer specifies 5W-30 and the oil meets the required performance specification.

Is 5W-40 good for diesel cars?

It can be suitable for diesel cars where the manufacturer specifies 5W-40 and the oil meets the required performance requirements.

Is 5W-30 better for mileage?

A lower-viscosity oil can contribute to fuel-efficiency objectives in engines designed for it, but actual mileage depends on many factors.

Is 5W-40 better for old engines?

Not necessarily. Engine age alone should not determine oil viscosity. Follow the manufacturer's recommendation and consider the engine's condition.

Can I change from 5W-30 to 5W-40?

Only if the manufacturer specifies or permits 5W-40 for your engine.

Can I use 5W-40 instead of 5W-30?

Only when the vehicle manufacturer's specifications allow 5W-40.

What is more important: 5W-30/5W-40 or API specification?

Both are important. SAE indicates viscosity, while API and other specifications provide information about performance requirements. Always match the complete specification required by your vehicle.

Final Verdict: 5W-30 or 5W-40?

The choice between 5W-30 and 5W-40 should not be based on which number sounds better or which oil feels thicker.

Both are useful engine-oil viscosity grades for applications that specify them.

The right selection depends on:

Your vehicle manufacturer's recommendation

Required SAE viscosity

API/ACEA specification

OEM requirements

Engine type and application

If your car requires 5W-30, consider the BHARAT Semi Synth MGEO 5W-30 SST.

If your car requires 5W-40, consider the BHARAT Semi Synth MGEO 5W-40 SST.

Always verify the vehicle manufacturer's requirements before purchasing or changing engine oil.

Explore Bharat Lubricants Engine Oils

Bharat Lubricants provides a range of automotive and industrial lubrication products designed for different applications.

Explore the Bharat Lubricants Engine Oil range to find products for different vehicle requirements.

For more automotive lubrication guides, engine oil information and maintenance tips, continue exploring the Bharat Lubricants blog.

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About Bharat Lubricants

Established in 1984 in Surat, Gujarat, Bharat Lubricants manufactures a wide range of automotive and industrial lubricants. Its product portfolio includes engine oils, gear oils, hydraulic oils, industrial oils, greases, coolants and other lubrication solutions.

Bharat Lubricants focuses on quality, application-specific lubrication and reliable solutions for customers across India.

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