Is Thinner Or Thicker Motor Oil Better?

Disclaimer: participant in the Amazon Associates Program. This means that qualifying purchases made through our links may result in a commission for us. This no extra cost to you.

It’s no secret that motor oil is an essential lubricant for your car’s performance. The correct lubricant is necessary to keep your vehicle running smoothly and avoid expensive repairs. Motor oil (AKA engine oil) is a complex lubricant consisting mainly of base oil and additives. So what does the latest engine oil technology have to say about the debate over whether thinner or thicker motor oils are better?

There is a lot of debate on thick vs thin motor oil. Many believe lighter oil is better because it flows more easily and prevents engine parts wear. Some mechanics believe more viscous motor oil is better because it absorbs more heat, prevents engine damage, reduces friction, and overheats.

This article will cover whether thinner or thicker motor oil is better for engines. Moreover, covering “engine oil too thin symptoms” and too thin symptoms and more about the viscosity.

Motor Oils
Motor Oils

Why Are Motor Oil Viscosity Grades Important?

The engine contains many metal-to-metal contacts. When the engine runs, these metal parts create friction, which causes wear and heat on them. Motor oil helps to reduce friction and temperature on these metal parts. At this point, motor oil viscosity plays a significant role. When viscous oil lubricates these moving metal parts and creates a thin film, it reduces friction and helps to lower wear and temperature.

The Society of Automotive Engineers (SAE) grades motor oils depending on the oil viscosity level. Some engine manufacturers recommend specific viscosity grade oil, while others suggest a range of SAE grades of lubricant. Choosing the right type of motor oil for your engine is critical, and viscosity is motor oil resistant to flow.

Motor oil viscosity chart


Thick vs thin Motor Oil.

Thicker oils perform better in high temperatures because oil thins out slowly at high operating temperatures and reduces friction. Moreover, viscous oil has high resistance to flow at cold temperatures, which increases cold start friction.

While thinner oils quickly flow at lower temperatures, they reduce cold start metal parts friction and offer better fuel economy but thin out at high operating temperatures. However, thicker motor oil consumes more fuel than thinner oil because of its high resistance to flow. As the temperature of the oil increases, its viscosity gradually decreases.

High-performance engines operate under greater loads on their parts, requiring higher viscosity and stronger oil film to protect parts. Therefore different engines are tuned to different viscosity of motor oils.


Thinner or thicker motor oil comparison.

The following tables give a better understanding of thinner or thicker motor oils.

Thick Motor Oil.Thin Motor Oil.
Fuel ConsumptionHigh.Low.
FrictionA cold start initially increases friction.A cold start prevents friction.
Engine start-upFlow slowly.Flow quickly.
High temperatureSlowly thin out.Quickly thin out.
Lubricant film strengthHighLow


Do all motor oils contain additives?

Generally, all types of motor oil contain up to 25% additives; the rest is base oil. Different lubricant manufacturers use different percentages of additives to improve the quality and performance of the base oil. These oils are developed to reduce metal parts wearing, friction, corrosion, and degradation and improve viscosity, gas mileage, and performance at high and low temperatures. Lubricant manufacturers mix different additives to improve the oil performance and quality, like aluminum, molybdenum, potassium, boron, sodium, calcium, magnesium, phosphorus, and zinc.

According to the American Petroleum Institute’s motor oil API service classification, different viscosity grades have similar additives. Therefore in the same API service category, thick and thin motor oils have the same additives to protect engine parts. But the mixing ratio can be changed.


Is thicker oil better for an engine?

There is no definite answer for thicker oil is better for an engine. Because it depends on the engine-built technology. Modern advanced engines are designed with tighter clearances between the engine’s crank journals and main bearings. Therefore lower-viscosity thinner motor oil flows quickly and provides better lubricant film in metal parts. This will reduce moving internal parts friction and improve fuel economy more than higher-viscosity oils.

If there is an increased clearance between crank journals and main bearings, it needs a thicker oil to fill these gaps. Most of the older engines have slightly increased clearance between engine parts, and in this situation, more viscous motor oil provides better lubricant film between moving metal parts. Regular high load is one of the reasons when to use thicker oil.


Motor oils


Should you use a thicker oil when towing?

When towing, the engine needs more torque and operates under high temperatures. If you are frequently towing and running in a warmer climate (summer), you need to use slightly thicker oil. Under a heavy load in warmer temperatures, slightly more viscous oil improves engine performance. If the engine manufacturer recommends a range of motor oil grades, you can use somewhat thicker oil when towing.

If you are not regularly towing, you should not use slightly thicker motor oil, which is an unnecessary expense. Towing heavy loads daily reduces motor oil life, and this engine needs high-viscosity motor oils. 



Will thinner oils damage the engine?

One of the most common questions asked by motorists is, “Will thin oil damage my engine?” The short answer is that there is no definitive answer as it depends on the specific oil and its use. However, some research suggests that using thinner oil may benefit your car’s engine.

Because thinner oil flows faster through your engine, it improves fuel economy. Additionally, lighter oils reduce wear and tear on the engine over time. There are a few things to keep in mind before switching to a thinner oil: First, make sure your car has been properly serviced and that you have replaced any worn or damaged parts. Second, ensure you’re using the right type of thin oil for your engine; Not all thinners are equal. Finally, follow the manufacturer’s instructions to avoid overfilling your car’s engine using lighter oil.



How to Pick the Best Motor Oil for Your Car or Truck.

Here are some tips to help you choose the right type of oil:

  • Use engine manufacturer recommendation: You must check your car’s manual to see what oil is recommended for your make and model. For example, if you have a Honda Accord, you should use Honda-specific engine oil. Not all Honda engines require the same type of oil, so it is essential to read the owner’s manual carefully.
  • Check the ingredients: Before purchasing, check the lubricant bottle label for its additives. We can find minerals, synthetic blends, and full synthetic motor oils. Different manufacturers use different additives to improve performance, and adding too many additives can create thick and heavy oil.
  • Engine load and climate: if the engine is under a heavy load and operates in a warmer climate, it needs slightly thicker oil. If the engine manufacturer recommends a range of oil grades, use the thickest one.


Thinner or thicker motor oils


Engine oil too thin symptoms.

Over time, engine oil degradation. This is because of high temperature,  contamination, oxidation, and additive depletion. The main symptoms of too thin motor oil are,

  • Leakage in a journal bearing.
  • Oil burning smell.
  • Discoloration.
  • Engine ticking.
  • Low oil pressure symptoms like Oil Warning Light.
  • Unusual engine noise.
  • Overheating.



Engine oil too thick symptoms.

Too thick motor oil causes many problems. If engine oil is too thick, your engine may not start in cold climates. This is because engine moving parts are not properly lubricated.

  • Struggles to start in cold weather.
  • Reduce fuel economy (reduced gas mileage).
  • Motor oil leakage.
  • Increase engine heat.



What happens if engine oil is too thick?

Engine oil can be thick for two reasons; you may use thicker engine oil or not follow the correct motor oil change interval. This will increase moving metal parts friction, struggle to start the engine, damage the oil filters, reduce fuel economy, and may result in costly repairs.

You may experience these issues because oil flow very slowly; it takes a few seconds to lubricate the pistons, so moving metal parts create friction and generate more heat. If the engine manufacturer recommends 0W-20 oil and you use 20W40, it is considered too thicker motor oil.


Does engine oil get thinner over time?

Engine oil gets thinner over time due to oxidation. This is the main cause of motor oil degradation. When base oil reacts with oxygen, it increases molecules size and weight, leading to sludge formation and deposits. Other causes include thermal breakdown, contamination (moisture and other oils), and additive depletion. This degradation increases motor oil viscosity and darkens the color. Degraded oil does not provide enough protection for engine parts; therefore, it is necessary to change the motor oil for better performance and protection of your engine. Most high quality motor oils include anti-oxidation additives to slow down the oxidation process.


Can engine oil affect fuel consumption?

Yes, engine oil can affect fuel consumption. When the oil gets thinner, it reduces oil consumption by around 1%. The reason for this fuel consumption is thicker oil flows slowly. When the engine starts, it pumps oil and flows to the engine to lubricate its parts. When the oil gets thicker, it flows slowly and takes more energy to pump. Accordingly, engine oil’s grade affects the fuel economy (thicker oil consumes more fuel than thinner motor oil). However, you should always follow the car manufacturer’s recommendation. Always use the manufacturer-recommended thinnest oil for better fuel economy and to protect engine parts.



All the engines are not the same; they develop to meet specific performance levels. Therefore, different engines require different viscosity grade motor oils to meet that performance level. Every engine manufacturer mentioned recommended SAE motor oil grade in the user manual.

If you use the wrong motor oil grade, it can negatively affect your vehicle. For example, if the engine manufacturer recommended 5w20 and you use 10w40 motor oil, it is harder to pump oil, so your fuel consumption can be increased, but it reduces the metal parts wearing.

Using a higher or lower number of cold and hot temperature ratings of motor oil can negatively affect engine efficiency. If your manufacturer recommends a series of grade oils, use thinner oil for better fuel efficiency. It is better for your engine life. And use thicker oil when towing. For better protection, use multi-grade motor oils, and that oil performs better in cold and hot climates.

Subscribe to Cars Reborn

Get latest posts to your email inbox.

Thank you for subscribing.

Something went wrong.

Leave a Comment!

This site uses Akismet to reduce spam. Learn how your comment data is processed.

error: Content is protected !!

Get more stuff like this
in your inbox

Subscribe to our mailing list and get interesting stuff and updates to your email inbox.

Thank you for subscribing.

Something went wrong.