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5w30 Vs. 5w40: Which Oil Is Better?

One of the most common procedures performed on a vehicle is an oil change. Whether you are a DIY’er who will perform this on your own, or someone who would prefer to have this done by a professional, choosing the correct oil is important. There are many and more choices when it comes to oil. This article will discuss the similarities and differences between 5w30 and 5w40

Factors To Consider When Choosing Your Oil

When considering which engine oil to choose there are several important factors to consider. First and foremost check the owner’s manual for the manufacturers recommendation. This is the oil that will work best, as it is what your engine was designed to use. 

At higher temperature, 5W40 will still be thicker than 5W30.
5w40 will remain thicker at higher temperatures than 5w30.

Another factor to consider when choosing between 5w30 and 5w40 is the temperature that the oil will be operating in. 5w40 will remain thicker at higher temperatures than 5w30. This could potentially offer better engine lubrication at these temperatures, but also could result in higher oil pressure

Also, how heavy of a load the engine will normally operate under should be considered. 5w30 and 5w40 will have the same viscosity and level of protection while cold, but when operating under more severe loads, 5w30 could offer less protection to your engine than 5w40. 5w40 will remain more viscous than 5w30 and help retain oil pressure when under a very heavy load. 

5w40 Engine Oil

Some features of 5w40 engine oil are:

  • Better protection at higher temperatures
  • Could help to reduce oil consumption versus 5w30
  • Easy engine starting in low temperatures
  • Help increase oil pressure in certain applications

5w30 Engine Oil

Some features of 5w30 engine oil are:

  • Good overall engine protection
  • Easy starting in cold weather
  • Potentially better fuel economy compared to 5w40
  • Easier internal oil flow at higher temperatures (could lower oil pressure)

What Is The Similarity Between 5w30 And 5w40 Oil?

5w30 and 5w40 engine oils have some similarities:

  • They both have the same viscosity rating in cold temperatures. The 5w represents how well the oil will flow through the engine when cold. Both engine oils are rated at 5, so they will offer the same flow and protection in colder operating conditions. 
  • Both are approved by many auto makers for use in their respective engines. 

What Is The Difference Between 5w30 And 5w40 Oil?

There are a few important differences between 5w40 and 5w30 motor oil.

  • Warm temperature viscosity. 5w30 will be thinner than 5w40 in higher temperatures, possibly reducing oil pressure and giving less engine protection.
  • Fuel economy. With 5w30 being thinner and easier flowing at high temperature, it creates less resistance between the moving parts inside your vehicle’s engine. This results in slightly higher fuel economy, as the engine does not have to work as hard to move these parts while driving. The opposite is true for the thicker 5w40.
  • Price: Generally speaking, 5w30 is more expensive than 5w40. 

Can I Use 5w40 Instead Of 5w30?

In most applications using 5w40 instead of 5w30 is perfectly acceptable. It is very likely that you will not notice any difference in a healthy engine. Most late model cars and trucks use variable valve timing and lift, which is controlled by engine oil pressure. On these cars it is important to use whichever viscosity the manufacturer recommends, as different thicknesses can affect oil pressure, thus affecting how these systems funcion. 

On older cars and trucks where these technologies were not used, the two oils are basically interchangeable. 

Can You Mix 5w30 And 5w40 Oil?

It is a best practice to not mix engine oils of different viscosities. In the short term it will not cause any engine damage, so topping up a car that is low on oil with a different viscosity is acceptable. However, it shouldn’t be used long term. I would recommend getting the oil changed and filled with whatever oil the manufacturer calls for as soon as possible to avoid any potential damage. 

As with everything vehicle related, it is best to follow the recommendations in your owners or service manual. Extra care should be used when selecting an engine oil if your car is equipped with VVT, because differences in oil pressure affect this system. But overall, if your car calls for 5w30 but it is not available or you don’t want to spend the extra money, 5w40 will be a suitable alternative.

Read more: 10w30 Vs 5w30: Can I Use 10w30 Instead Of 5w30?

Michael Griskauskas

Michael Griskauskas is an ASE Certified Master Technician who started his automotive career in 2004 after graduating from the Baran Institute of Technology with a degree in Automotive Technology. He is a factory trained Fiat/Chrysler technician, although he has spent the majority of his career in the aftermarket. With a focus on imports, he enjoys the challenge of keeping up with the ever-changing technology and diagnostic techniques within the industry.

Web: http://obdadvisor.comEmail: mgriskauskas@gmail.com
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