5W30 vs 5W40 : Which Oil Should I Choose?

Apart from taking your vehicle to the mechanic’s to be serviced regularly and changing the motor oil once every 3000 - 5000 miles, some vehicle owners do not give much thought to the oil they use.

As a matter of fact, you should pay attention to your motor oil and the type you use in your engines. We will tell you why just below.

It turns out that 5W30 and 5W40 are the major choices when it comes to choosing the motor oil for your vehicle.

What is the difference between them?

And which one should you use?

We will tell you.

Product

Product Name

Our Rating

Price

"Best Pick"

Royal Purple SAE 5W-30

Royal Purple SAE 5W-30

"Top Selling"

Shell Rotella T6 Full Synthetic 5W-40

"Affordable"

Mobil 1  Synthetic Motor Oil 5W-30

Why Should You Choose the Right Oil?

Motor oil plays a very important role in the running of our engines. If not we won’t be getting warning signals telling us the oil level is low.

What exactly does the oil do in the engine?

1

Reduce Wear and Tear

Your engine consists of moving parts mostly made of metal. When they move or rotate, they rub against each other. This causes their surfaces to wear out and tear. Oil helps reduce this wear and tear by lubricating those surfaces.

2

Prevent overheating

Because oil reduces the contact between two moving parts, it helps reduce the chances that your engine will overheat.

3

Protects your engine from rusting

Combustion happens inside your engine, that’s why it is called an internal combustion engine. This combustion needs oxygen in the air to work. This air has water vapor in it. When oxygen and water vapor comes in contact with metal, rusting is the result. Motor oil helps protect metal surfaces from rusting.

Without the right oil running in your engine, your engine can fail, overheat and cover you in smoke or need replacement parts way too often.

If you manage to escape some of these serious issues, you may experience your engine performing poorly. For example, engine parts are delicately designed with precise measurements. Wear and tear can reduce these originally engineered measurements and lead to your engine performing less than the manufacturers designed it to.

The Science Behind It

What is the meaning of “5W30”? Let’s dissect it.

The Society of Automotive Engineers (SAE) made it a standard for motor oils to be identified with a code that signifies their viscosity.

From lowest to highest, they are: 0, 5, 10, 15, 20, 25, 30, 40, 50, and 60.

#1. Viscosity/Thickness of the Oil

This is used to describe a liquid’s resistance to flow. Fluids with low viscosity are like water, they run and flow easily. Meanwhile, highly viscous fluids are thick and flow slowly like wax from a candle.

#2. Weather and How it Affects the Oil

Now, what does the W in 5W30 stand for? It simply means “winter”.

This is necessary for the code because temperature normally affects how easily a liquid will flow (it's viscosity, remember?). Your oil needs to be light enough to flow at low temperatures (winter) and also thick enough to keep your engine working optimally.

Single Grade Oil vs Multigrade Oils

Not a lot of people address this topic, but if you are really intent on knowing your motor oil, this is something to note.

Single Grade

For older cars, the manufacturer normally recommends single grade oil. A can of single grade oil is easily identified because it indicates only a number, followed or not by the letter W.

This oil only has one viscosity, irrespective of the operating temperature in the engine.

The disadvantage of Single Grade Oils

They can only be used in narrow temperature ranges. That means the single grade oil that served you in winter will be bad for your engine in summer.

Multigrade Oil

Unlike single grade oil, multigrade oil has been designed to have a viscosity that changes with temperature. This is done so that at lower temperatures, the oil flows more freely but at a higher temperature, it thickens. It is mostly used for modern cars.

What this means is: when you turn off your vehicle, all the oil goes down into the crankcase of the engine. When you start it up again, it takes only microseconds before the oil flows throughout the entire engine.

Advantages of Multigrade Oils

  • Multigrade oils flow more freely at lower temperatures, this helps the oil reach all parts of the engine quicker than single grade oil would in the same conditions, reducing start-up wear.
  • When compared to single grade oil, multigrade oil saves up to 3% fuel
  • A multigrade oil provides better protection for low and high-temperature engines than a single grade oil as it maintains optimum viscosity over the engine's operating temperature range.

The disadvantage of Multigrade Oils

Multigrade petroleum products can lead to oil leakage during low-temperature situations if the engine is worn. Stress and high load conditions on the vehicle can also lead to polymer shear.

Now, what is the difference between 5W30 and 5W40?

Differences Between 5W30 And 5W40

5W30​​​​​​​

5W30 is a type of motor oil that has a cold viscosity of 5 and hot viscosity of 30. It is a multigrade oil. What this means is that in cold temperatures (like in winter), your 5W30 oil will flow much more freely at the SAE viscosity grade of 5 and thickens up to 30 in hot weather.

This synthetic lubricant can be used in temperature conditions ranging from -30 ° to + 35 °. This is one of the widest ranges; the most extensive of all (from -25 °; + 50 °) is that of oil 10W60.

Here are some advantages of 5W30 motor oil:

  • Fuel economy
  • Easier start
  • Latest generation engine
  • Particulate filter protection (FAP)
  • Catalyst protection
  • Extreme engine protection
  • Low and high temperature protection
  • Environmental Protection
  • Long drain intervals

5W40

As with 5W30, 5W40 motor oil has a cold viscosity of 5. The major difference between them is that 5W40 has a hot viscosity of 40. It means at higher temperatures, it will be thicker than its counterpart of hot viscosity 30.

Some advantages of 5W40 oil are:

  • Easier start
  • High performance engine
  • Catalyst protection
  • Severe use
  • Long drain intervals

5W30 vs 5W40

They both have their strong points and weak points. But when placed side-by-side, which one trumps the other?

Many professionals would recommend 5W30 for a good reason: it is much more versatile in use. Unlike 5W40 which is not as popular but cheaper.

In their own way (and right applications), both serve the purpose of quickly lubricating your engine and dissipating heat which, fundamentally, is the purpose of oil in the engine.

In summary,

Comparison Table of 5W30 & 5W40

Properties

5W30

5W40

Viscosity (High-shear rate)

2.9 at 150g

3.5 at 150g

Viscosity (Low-shear rate)

9.3 – 12.5mm2/s at 100g

12.5 – 16.3mm2/s at 100g

Temperature range

-25 to 25

-25 to 35

Thickness

Lighter

Heavier

Oil Flow

More

Less

Cost

Expensive

Cheaper

Fuel Economy

Great

Poor

Application

Versatile

Less popular

Which One Should I Choose?

If your vehicle has a particulate filter, you should go for 5W30 motor oil. If not, 5W40 will work just fine with your engine.

Conclusion

Now that you know what you know, is 5W30 the best motor oil for your vehicle?

Yes and no.

Yes, considering its properties and capabilities, it is clearly superior. On the other hand not always, because a good oil is not a powerful oil but rather the oil which is best adapted to the engine.

An old engine is designed to work with older oils with different properties. Putting a high-quality modern oil in an old vehicle will be harmful despite the more advanced properties.

Jose Wagner
 

I am Jose Wagner, a mechanic who loves exploring & writing about new tools and contraptions which make everyone’s lives a whole lot easier. I have been in the manufacturing industry for several years and possess sound mechanical knowledge and diagnostic skills.

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