0W20 vs 5W30 Oil: Things Manufacturers Don’t Tell You


According to the “Society of Automotive Engineers (SAE)”, 0W-20 and 5W-30 are two separate grades of engine oils. They serve the same functions such as reducing friction between engine parts, minimizing wear, and keeping the engine free of sludge and varnish.

Then, why should you bother about anything that reflects 0W20 vs 5W30? Despite sharing some similarities in chemical properties, these oil grades are different. In this article, you’ll get the underlying and comparative facts about them, so you can choose wisely for your vehicle.

0W20 vs 5W30 Oil: A Quick Look at the Determining Factors

Here is a table to let you find out what differentiates one grade from another. For experienced people, the table should make sense, but beginners may look for more details.

0W-20 Oil5W-30 Oil
Good oxidation and thermal stabilityBetter thermal stability in unpredictable temperatures
Better protection against frictions in normal driving conditionsBetter protection against frictions and particles in extreme conditions
Quicker start and lubricationSlower start and lubrication
Lower fuel consumption but costlierLess expensive and readily available
Longer intervals between oil changesImproved protection against rust on engine parts

Several considerations come into play when the performance of an engine oil is to be evaluated. The most important ones include:

  • Viscosity properties in different temperatures
  • Protection against corrosion and wear
  • Ability to yield strength under levels of compression
  • The way it accommodates abrasives, soot, and other particles in suspension and keeps the car engine clean

The first point of the list is the key to your understanding of engine oils. We’ll discuss this before explaining the other three points.

You’ll see certain numbers which represent viscosity. Those numbers state the quality and properties of an engine oil better than others. It helps you tell which oil behaves in what way facing a specific temperature. Thus, you can ensure that your car engine gets the right lubrication based on the changes in weather conditions during operation.

Understanding the Numbers

You can use a bit of explanation to understand why these two grades are different. Let’s break down the numerical code system introduced by SAE. 0W-20 and 5W-30 contain three parts such as “0”, “W”, and “20” or “5”, “W”, and “30”. These numbers indicate the thickness and weight, or viscosity of these oils which get thicker in cold temperatures and thinner in hot conditions.

The first numbers are 0 and 5. They indicate viscosity at the startup of the engine (when the temperature is cold). The second numbers are 20 and 30 which also indicate viscosity but when the engine is active and the temperature is high. The W letter stands for “winter”, not “weight”.

Oils with lower numbers are thinner and indicative of lower friction. In addition, thinner oils at engine startup account for good cold-start performance. Considering these facts, you can arrive at a conclusion like this:

0W-20 oil flows as smoothly as a 0-weight oil in cold temperatures. Even in winter temperatures, oil doesn’t have any difficulty flowing through its designated way immediately and supplying lubrication to the critical parts of the engine. With the engine reaching its operating temperatures, it starts flowing like a 20-weight oil and thinning out faster than a 30-weight oil.

You might think you can always do better off using the thinner oil, but there is more to the debate. 5W-30 is a multigrade engine oil that works reliably under a wide range of circumstances (temperatures).

Not only does it flow well in cold conditions, but also it lubricates the car engine satisfactorily. Another perk of using this oil is that it takes more time to thin out and offers greater resistance to loads than 0W-20 oils.

Viscosity affects the time required by the oil to circulate in the engine. Depending on how hot or cold your vehicle’s engine is, the duration can be as short as 3 seconds and as long as 20 seconds or more.

Now, you see how the viscosity of each oil sets them apart. So far, all you’ve got is a basic idea that may help you make a choice, but you need more details to get a full picture of their efficiency.

Understanding the Performance and Properties

Like any motor oil, 0W20 and 5W30 are formulated engine oils consisting of mineral, base oil, and additives in varying numbers and concentrations. The base stock can be semi or fully synthetic, and the quality of any oil depends mostly on it. The additives also impact the oil’s overall efficiency.

Thinner oils like 0W-20 feature less drag which results in less friction and gradually less wear. That is true when your car is exposed to normal operation. It is also practically viable for test engines.

But thicker oils like 5W-30 may prove to be better at providing protection when a car is intended for more intensive operations. Can you guarantee that you won’t drive the car through mountains or dusty trails? Is it always easy to avoid conditions like overloading, overcooling, or overheating? Put your car in any of these situations, and it’ll do better with thicker oils.

An engine oil creates an oil film. If any abrasive particle is too large for the thickness of the oil, it will eventually cause wear. Filters can be good enough to keep the size of those contaminants small. You still want to consider oil film thickness because thicker oils create thicker films which can hold larger contaminants.

Which Grade Is the Better of the Two?

Manufacturers keep recommending thinner oil grades using only one excuse – fuel economy. Do you accept that? As you know lower viscosity is associated with decreased frictions which help improve fuel economy and support efficiency, you may have realized why the 5W-30 grade is giving place to the 0W-20 grade.

You shouldn’t get surprised to see fewer new cars specifying thicker grades. However, no substantial evidences are available to support the claim that one is superior to another when it comes to engine life.

Final Words

This discussion will come to an end with the answer to a very common question “Can I use 0W-20 when it says 5W-30?” Car owners often ask this. Well, every owner’s manual has a certain oil type specified in it, but using one in place of the other may not always cause harms.

So, picking up one of these two oil grades is not easy if you stick to one consideration. You have to think about the climate you’re driving in, count the number of years the engine is running, and review your purposes and driving habits.

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