Are Thinner Oils Bad For Your Engine?

Every day we see more and more engine oils with lover viscosity. Back in the day, it was pretty normal to use a 10w50 engine oil. Nowadays, oil companies strive to create engine oils with lower viscosity (weight). They claim that thinner oils are actually improving your engine performance and increasing the fuel efficiency. So the question here is ”Are thinner oils bad for your engine?”

What Do Oil Weights Actually Mean?

What Do Oil Weights Actually Mean

When people use the term oil weight, they actually refer to the viscosity of the oil and not the actual weight of the oil. Viscosity is essentially the thickness of the oil. So, the numbers on the oil can (10w30, 5w40, etc.) actually are a viscosity measurement. These numbers really identify as the oil’s viscosity grade.

Fluids like water and honey have a different viscosity grade. The honey is thicker and has a higher viscosity than the water. Ensuring the proper viscosity oil is used in your car is the single most important thing.

Apart from telling the ”weight” a.k.a viscosity of the oil, these numbers are also temperature-dependent. For example, if your engine oil is 10w30, these numbers represent the viscosity grade of the engine oil when it’s cold(10) and when it’s hot(30).

In this case, 10w30 engine oil is called multi-grade oil because there are two numbers. If the second number is larger than the first, it means that the engine oil gets thicker as it heats up.

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Is your engine oil due for a change? Visit our Car Fluid Guide Website to learn the importance of changing your oil on time, which type of engine oil is best for your vehicle, and much more.

Do Thinner Oils Improve Fuel Efficiency?

Generally speaking, thinner oils (engine oils with lower viscosity) improve fuel efficiency because of the lower friction. When the engine oil is thinner, it takes less energy for the engine parts to move when they come in contact with the oil. If the engine oil is thicker, it requires more energy for the engine to normally operate.

Think of it like this. It takes more energy for you to put your hand in honey and move it around, but it takes you less energy to put your hand in the water and move it.

There is a trend in the automotive industry where they strive to lower the viscosity of the engine oils. We see more and more engine oils with low viscosity. In fact, there are production cars sold with 0w16 engine oils. But, why are they doing this?

There is no obvious answer on how much thinner oil increases the fuel efficiency of your vehicle, but there are some studies showing that switching from a 30 to a 20 engine oil could result in over 1 increase in fuel efficiency.

Lower viscosity grades are required to meet more challenging fuel economy limits because it’s known that they improve efficiency based on these fuel economy tests. The difference between different engine oils is around 0.5 percent on average.

Fighting for a fraction of a percentage improvement in fuel economy may not sound significant for those who aren’t working within the field of internal combustion efficiency. But, when you consider how efficient today’s engines are, gas engines with peak efficiency around 40 percent raising that number to 41 percent.

Can Thin Oils Effectively Protect an Engine?

Thin oils can efficiently protect an engine as long as you change the engine oil at proper intervals, your engine is in good shape to begin with, the oil pump is maintaining a proper oil flow, and the proper oil is being used.

Companies have done an extremely good job of figuring out how to make the internals of engines last long. But, it is up to you to make sure that the engine oil is changed at regular intervals. This will prolong the engine’s life.

There are instances like when you start up the car that, you won’t have that full oil film thickness between the moving parts available. That’s when anti-wear additives are useful that stick to metal surfaces and minimize wear at startup.

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Hi there. I am a certified Automotive Service Excellence (ASE) mechanic since 2018 and a car detailer for 10 years.

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