10W30 Vs 15W40 Engine Oil

10W30 vs 15W40

If you’re in the market for new engine oil, you’ve probably noticed that there are two different viscosities: 10W30 and 15W40. What does this all mean? The oil’s viscosity determines how quickly it will flow. The lower the number, the easier it will flow.

If you’ve got a high-performance engine and want the oil to reach the bottom of the engine, you want the lower viscosity oil. You want the thicker oil if you’ve got an older car with a high-mileage engine.

15w40 vs 10w30 Table

The battle around 10w30 and 15w40 is natural as both are engine oils. According to the purpose, they have many similarities but differences in many other ways.

AmazonBasics Oil

Shell Rotella T

Ideal for engines over 75,000 miles

Meets or exceeds API CJ-4 requirements

It helps for longer drain intervals

Helps to keep longer engines drain interval

Prevent engine rust and corrosion

Formulated for enhanced deposit protection

it helps reduces engine wear

Wear control helps longer life.

Helps reduce exhaust emissions

Outstanding protection for all heavy duty diesel engines

High resistance to viscosity and thermal breakdown

Enhanced shear stability performance for viscosity control

For best performance, follow the manufacturer's recommendations

For best performance, follow the manufacturer's recommendations

Main Difference

The main difference between 10w30 and 15w40 is the viscosity. This is a measure of a fluid’s resistance to flow. The lower the number, the less resistance and easier it flows.

List Of Differences

  • 10W-30 is a synthetic designed for conventional engines and low-stress, extended drain intervals where it can be used in high concentrations for oil control.
  • 15W-40 is a synthetic designed for higher performance engines, with more stress and heat. It can be used in lower concentrations for oil control.
  • 10W-30 is the cheaper of the two oils. It has lower viscosity at extremely low temperatures.
  • 15W-40 is the more expensive of the two oils. It has greater viscosity at extremely high temperatures.
  • 10W-30 is better for all temperatures and conditions where the engine generates little to no heat.
  • 15W-40 is better for extremely hot conditions such as towing, hauling, and stop-and-go driving.
  • 10W-30 is better for protecting engine components for more extended periods between oil changes.
  • 15W-40 is better for active engine components, like oil pumps and bearings.

What Is 10w30 Engine Oil?

10w30 is multi-grade engine oil suitable for heavy-load engines due to its ability to endure high temperatures for an extended time without losing engine efficiency. In low temperatures, this engine oil has a viscosity rating of 10. In high temperatures, it has a viscosity grade of 30. This engine oil has a low viscosity at low temperatures, implying that it is thin.

The American Petroleum Institute establishes specific standards, and the oil you want to use on your car must first meet these requirements to be deemed fit for use. These conditions, including the API SN rating, are met by the 10w30, which effectively ensures that the engine can shield the piston from deposits created by combustion.

Sludge management is also used in 10w30. High temperatures lead to the failure to shape either sludge or gel. It is also compliant with aftercare and sealing. Finally, according to the European Automobile Manufacturers Association, it should have an ACEA A3/B4 or A3/B3 ranking.

Benefits Of 10w30 Engine Oil

10w30 has a variety of distinct characteristics and advantages. This engine oil forms a continuous coating over all of the engine’s components, reducing friction between them. They often minimize engine wear and tear while keeping the engine cool during the stop/start process.

10w30 prevents engine components from corrosion. This oil will help the engine last longer. It provides the customer with quiet and seamless gear and clutch operation. Also, at high temperatures, this engine oil maintains its viscosity.

It is appropriate for engines that run on advanced fuels such as biofuel and biodiesel. While 10w30 can be used in cold weather, it is best suited for use in hot weather.

What Is 15w40 Engine Oil?

15W-40 Engine Oil is a high-performance, synthetic plus, heavy-duty diesel engine oil designed to protect against wear, oxidation, deposit formation, soot contamination, and aeration.

Triple protection plus technology and its benefits are infused in 15w40 diesel engine oil. Triple Protection Plus is a one-of-a-kind blend of Triple Protection advanced additive manufacturing and synthetic base oils. Triple Safety Plus offers resistance to wear, deposits, and oil breakdown, as well as improved low-temperature flow. This synthetic blend oil protects machinery well, extends engine life, and retains viscosity regulation at high temperatures.

It provides excellent wear safety, exceptional deposit management/cleanliness, protection against oil breakdown, and long-term pollution control system reliability in particulate filters and after-treatment systems. 15W-40 Synthetic Blend is appropriate for a variety of heavy-duty engine applications.

It is an ideal option for on-highway fleets, manufacturing, agriculture, and diesel pick-up trucks, as well as high-power vehicles that need resistance to increased heat and tension. It offers the same safety as an SAE 15W-40 but in a synthetic blend of heavy-duty engine oil.

Benefits of 15w40 engine oil

  • This formulation of 15w40 has better oxidation performance and more excellent resistance to degradation at high temperatures.
  • Formulated to monitor engine wear, outperforming the overall wear specifications in API CK-4 engine wear tests by 37%2. (2 Calculated average based on API CK-4 wear test results)
  • Synthetic base oil elements are used to formulate this heavy-duty fuel oil.
  • Helps monitor piston deposits for increased engine efficiency at prolonged oil drain intervals1 (1 Shell Rotella T5 retains oil viscosity outside the OEM recommended drain interval; still observe the OEM’s recommended oil drain interval)
  • Compared to SAE 15W-40 oils, Triple Protection Plus technology protects against wear, deposits, and oil breakdown while improving low-temperature flow.


10w30 synthetic Small-Engine Oil is a shear-stable, high-film-strength solution reinforced with zinc anti-wear additives. It does not thin due to mechanical shear, resulting in a dense lubricating film. Its zinc chemistry creates a long-lasting shield that prevents metal-to-metal interaction. 10W-30 Full Synthetic Motor Oil can keep the engine in good shape and make it run at its best.

15w40 is a heavy-duty engine oil with triple plus protection. It helps improve the engine’s performance and ensures a longer lifespan of the machine. 15W-40 Synthetic Blend Technology performs much more than the current CK-4 standards require, providing 37% more wear resistance than the maximum wear criteria. Exceptional Cleanliness Several measurements show that 15W-40 diesel oil offers outstanding piston cleanliness, outperforming Mercedes and Volvo limits.

Oil Consumption

10w30s heat-resistant synthetic base oils have low volatility, excellent viscosity stability, and excellent oxidation resistance. Engines run longer between top-offs, giving you peace of mind that they will not crash due to oil starvation and can run reliably even under extreme circumstances.

The 15w40 oil provides excellent equipment protection and gives the engine long life. Also, it maintains viscosity control under high temperatures. However, this oil reduces the number of oil breakdowns under extreme conditions.


Engine wear, carbon deposits, valve, and piston ring limit engine strength. Synthetic Small-Engine Oil avoids ring and valve sticking while also assisting in the removal of carbon deposits. As a result, engines provide full power during their service lives, allowing you to do further tasks.

Engine 15W-40 Also, under rough, severe duty working conditions, oil ensures outstanding machinery reliability and longevity. 15W-40 forms a slick, tenacious barrier that protects against metal-to-metal touching. This additional reliability safety layer decreases wear on bearings, rings, pistons, valves, and valve trains. Heavy-duty diesel engine oil is designed to guard against wear, degradation, deposit formation, soot pollution, and oxygenation.

Our Observation

Both the 10W30 and 15W40 Engine Oil provides great benefits and performance to the engine. However, we recommend the 15W40 for heavier duty and more intense use. It will provide better protection against wear and tear, as well as offer improved cleanliness and oil consumption control. If you are looking for engine oil that will give you the best possible performance and protection, then we recommend the 15W40.

If you are looking for an oil that is more budget-friendly, then the 10W30 would be a great option. It still offers excellent protection and performance, but it may not be as durable as the 15W40 under more extreme conditions. Whichever oil you choose, make sure to follow the manufacturer’s recommendations for oil changes and maintenance to get the most out of your engine oil.

Frequently Asked Questions (FAQ)

If you’re looking for an oil that can withstand high temperatures and protect your engine against wear, 15W40 oil is a good option. This type of oil is typically used in heavy-duty diesel engines that operate under severe conditions. It can also be used in other types of engines, such as those construction equipment and farm machinery. 15W40 oil is available from most major oil manufacturers.
Yes, 10w30 is a good oil for diesel engines. It helps to keep the engine running smoothly and efficiently.
15W is thicker than 10W. This is because the W stands for weight, and 15 is heavier than 10. So, if you’re looking for a thicker oil, 15W is the way to go!
15W40 oil is good for use in a variety of temperatures. It has a high viscosity, which makes it ideal for use in cold weather. However, it also has a high pour point, which means that it can be used in hot weather without breaking down.



10w30 can be a good choice for both gasoline and diesel engines. It decreases the number of oil breakdowns under extreme conditions and ensures outstanding machinery reliability and durability. 15w40 performs much more than the current CK-4 standards, providing 37% more wear resistance than the maximum wear criteria. If you want to choose the best engine oil, keep all of these differential points in mind.

At the end of this article, we can say that there are certainly so many facts that differentiate these engine oils. So, keep the points that make them different whenever you want to buy them. If you do not know how to choose the best engine oil, read our differential points.


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