Best Oils for Duramax Engine in 2020

Duramax engines of different generations are distinguished by their stunning power and ability to run smoothly in the most difficult conditions. The average power of such engines is about 300-310 HP. To ensure proper and long-term engine operation, you need to use appropriate oils, which will not only start the engine fast but also provide its full protection in all weather conditions.

The best oils for Duramax engines are represented by synthetic versions, which allow loading the engine in both low and high-temperature conditions. New synthetic oils maintain fluidity and viscosity at a wide temperature range, so many drivers choose synthetic oils for Duramax. Such oils require less frequent changes compared to regular car oils, with Rotella T6 and Mobil 1 oils being the leaders. Such oils feature both a high-quality synthetic base and advanced additives.

Semi-synthetic oils are also used in Duramax engines of different generations. They feature an advanced set of additives that reduce oxidation processes and friction during engine operation. The leader among semi-synthetic oils is Delo 400 SDE. It’s used not only in truck engines but also for industrial and agricultural purposes Significant fuel economy, due to reduced resistance, makes this oil a reasonable choice for commercial needs.

The most optimal oil in terms of viscosity and temperature capabilities is 15W-40. It’s versatile, all-season oil that can be used in various diesel engines in moderate climates. When choosing the best oil for a Duramax engine, pay attention to the following points: viscosity at 212F (100C), solidify temperature, additives (to ensure minimum friction of engine parts), synthetic base, and fuel economy.

List of Top-Rated Oil for Duramax

Mobil Super 96819 15W-40 Delvac 1300Mobil Super 96819 15W-40
Delvac 1300
Royal Purple 04154 15W40Royal Purple 04154 15W40Synthetic
Rotella T6 Full Synthetic 15W-40Rotella T6 Full Synthetic 15W-40Synthetic
Delo 400 SDE SAE 15W-40Delo 400 SDE SAE 15W-40Semi-Synthetic

Reviews of the Best Oil for Duramax

Mobil Super 96819 15W-40 Delvac 1300 Motor Oil – 1 Gallon (Pack of 4)

Mobil Super 96819 15W-40 Delvac 1300 Motor Oil - 1 Gallon

Mobil Delvac 1300 Super 15W-40 is designed for powerful diesel engines. It is used not only in passenger cars and pickup trucks but also in agriculture and other industrial spheres. It’s a traditional refined mineralized oil, free of unnecessary impurities. It has a number of characteristics that make it one of the most productive oils for Duramax engines.

Firstly, Mobil Delvac 1300 Super 15W-40 protects the engine from corrosion. The oil is notable for its resistance to oxidative processes, which are most pronounced at heating. The oil not only keeps its density at high temperatures but also helps cool down the engine.

Secondly, it has sufficient fluidity to flow through the system at low temperatures. If the outside temperature is -4F, the oil will still allow starting the engine fast without harming it. In fact, it’s an all-season oil, which protects the engine in any weather.

Thirdly, the product does not require frequent changes. Compared to other conventional oils, Mobil Delvac 1300 retains its properties 1.5 times longer and can be replaced after about 30,000 km. Of course, the oil condition should be monitored, since the need for its replacement depends on the condition of the vehicle, loads, and driving conditions.

The flashpoint of the oil is 437F. It can be safely used during hot weather at heavy engine loads, as it retains its viscosity at 212F with 14 units. As for the solidify temperature, it’s -27.4F.


  • All-season oil for powerful diesel engines
  • Great fluidity at low temperatures
  • Versatile application
  • Cools down the engine at heavy loads
  • Complete protection for Duramax engines
  • High oxidation stability


  • Manufacturer: Mobil 1
  • Viscosity: 15W-40
  • Capacity: 3.78 liters
  • Oil type: mineralized
  • Weight: 1 pound

Mobil Delvac 1300 Super 15W-40 has long been used for commercial and industrial purposes, as it is the most optimal in terms of price and quality. It’s perfect for powerful Duramax engines and is available in 3.78-liter black branded gallons.

How much oil do I need for a complete replacement in my Duramax?

Duramax engine is about 9.46 liters, thus, you will need 3 gallons of the oil. The oil change is best done at a service shop.

What means “Delvac” in the oil name?

Delvac is an acronym that is also a registered trademark. It stands for Diesel Engine Lubricant VACuum oil. This indicates that it’s diesel oil, used in a vacuum environment, and providing protection when the engine is running. 

Royal Purple 04154 15W40 Oil One Gallon

Royal Purple 04154 15W40 Oil One Gallon

Purely synthetic oils have long proven to be more versatile and durable compared to other regular oils. Synthetic oil with the right set of additives provides full engine protection in all operating conditions. Synthetic oils can be changed less often than mineralized oils. According to Royal Purple, their oil can be changed after running from 8,000-10,000 thousand miles. This is a very impressive interval, as most oils will require replacement after 3,000-5,000 miles.

Royal Purple 04154 15W40 uses a synthetic base with additives to reduce friction. As a result, the engine retains its original performance, wear is reduced, and fuel efficiency becomes more noticeable. The oil protects the engine at all temperatures, as its density, fluidity, and viscosity are preserved. When heated heavily, the oil has strong antioxidative properties.

The oil solidifies at -22F. In this case, the engine can turn the crankshaft at -4 degrees but constant operation at this temperature is undesirable. At high temperatures, everything is much better – the oil retains all its protective features when heated even over 212 degrees. This is evidenced by the 15W-40 marking, which indicates that the oil is all-season and can be used for different types of engines.


  • Unique additives for extra engine protection
  • Full compatibility with other similar oils
  • Enhances fuel efficiency
  • High anti-corrosive properties
  • Reduced friction of engine parts


  • Manufacturer: Royal Purple
  • Marking: 15W-40
  • Capacity: 3.78 liters
  • Oil type: synthetic
  • Set Weight: 7.68 pounds

Royal Purple products are always of excellent quality. This 15W-40 oil is suitable for diesel engines, providing full protection during intensive loads. The price of the oil may seem quite high but its quality speaks for itself. The oil is produced in violet Royal Purple 3.78-l gallons, which allows you to distinguish the original product from a fake. To fully change the oil in a Duramax will require a few gallons of this oil.

Is this oil suitable for old Duramax engines?

This oil works perfectly with diesel engines, including Duramax. If the engine is no longer new but is still in working condition, the synthetic oil presented can be safely used. If the engine is worn, it makes sense to use mineralized or semi-synthetic oils depending on its condition.

What is the viscosity of this oil at 212F?

Oil viscosity at 212F is in the range from 13-15 units, which indicates high density of the substance when heated, as well as efficient engine protection at constant heavy loads.

Rotella T6 Full Synthetic 15W-40 Diesel Engine Oil (1-Gallon, Case of 3)

Rotella T6 Full Synthetic 15W-40 Diesel Engine Oil (1-Gallon, Case of 3)

Rotella T6 Full Synthetic 15W-40 Diesel Engine Oil is a high-tech product, which brings engine performance to a new level. It’s a fully synthetic oil with special additives for effective wear reduction. This substance also fully protects the engine from oxidation processes. The oil effectively removes dirt particles and soot without causing oxidation, which helps keep the engine in its primary state.

When heated heavily, the oil does not lose its viscosity. Moreover, its density is sufficient to create a dense and uniform layer between engine parts, resulting in minimized friction and reduced wear. According to the manufacturer, the oil shows 3 times higher productivity, compared to other 15W-40 oils. 

This is all-season oil that keeps the engine safe at low temperatures and retains enough viscosity when heated.

The oil also increases fuel economy and ensures correct engine operation. Studies show that using this oil improves fuel efficiency by about 1.5%, compared to other oils. On an industrial or commercial scale, this can significantly reduce overall fuel expenses.

Rotella T6 is used not only in Duramax engines but also in other diesel engines. It can also be a passenger car engine, a marine engine, or an industrial engine. It’s the most versatile, commercial oil with the most productive characteristics.


  • Helps save on fuel
  • Prolongs engine life
  • Retains its density and viscosity at high temperatures
  • Features additives to ensure complete diesel engine protection
  • Broad application


  • Manufacturer: Shell Rotella
  • Marking: 15W-40
  • Capacity: 3,785 liters
  • Oil type: synthetic
  • Weight: 23.7 pounds

Shell Rotella T6 5W-40 Diesel Engine Oil retains its viscosity at high temperatures with a kinematic viscosity index of 14.7. The oil can withstand heavy loads because and its flashpoint is 480,2F. The oil is designed for industrial applications and has all the necessary properties. It’s stable at low ambient temperatures and solidifies only at -38.2F.

Shell Rotella T6 5W-40 Diesel Engine Oil is produced in signature blue 3.785-liter gallons with the corresponding marking. This particular set includes 3 gallons of oil.

How can engine oil reduce fuel consumption?

Energy saving oils are relatively new. Their efficiency depends on optimal viscosity, which, on the one hand, must keep the engine safe at all conditions and, on the other, provide minimum resistance because decreased resistance means decreased fuel consumption.

Delo 400 SDE SAE 15W-40 Motor Oil – 1 Gallon Jug, (Pack of 3)

Delo 400 SDE SAE 15W-40 Motor Oil - 1 Gallon Jug, (Pack of 3)

Delo 400 SDE SAE 15W-40 with ISOSYN Advanced Technology has the widest application in any diesel engine, including Duramax engines. The company’s products are distinguished by high quality and special technologies, which allow obtaining excellent protection means for powerful engines. The oil under consideration is used in industrial machinery, marine vessels, and agricultural machinery.

Delo 400 SDE SAE 15W-40 effectively copes with used particles, reducing friction inside the engine. It meets all modern requirements for purity and efficiency, plus, it can also be used with exhaust aftermarket systems. The product is perfect for new and old 4-stroke engines that require compliance with API CK-4 or SN standards. This oil maintains the right viscosity at high and low temperatures, providing all-season protection for commercial diesel engines.

When heated to 212F, the kinematic viscosity of this oil is 14.6 units, which not only provides the necessary coating properties for the necessary engine parts but also helps reduce friction and resistance between them, resulting in improved fuel economy. The flashpoint occurs at 442F, and the oil solidifies only when the temperature is lower than -27.4 degrees.


  • Versatile oil for all diesel engines
  • Meets the requirements for exhaust emission reduction
  • Suitable for fuels with low and normal sulfur content
  • Lower fuel consumption
  • API CK-4 or SN compatibility


  • Manufacturer: Delo
  • Marking: 15W-40
  • Capacity: 3,785 liters
  • Oil type: semi-synthetic
  • Weight: 23.9 pounds

Delo 400 SDE SAE 15W-40 for diesel engines uses the most advanced additives, providing full protection for industrial engines, and helping its owners save on fuel consumption. The oil is released in blue 3.8-l gallons, in 3-piece packs. It’s suitable for any engine where API CK-4 or SN specification is specified.

What fuel does Delo 400 SDE oil work best with?

Delo 400 SDE SAE 15W-40 provides engine protection with any fuel, including biodiesel. It has high antioxidizing properties and reduces engine wear. The manufacturer states that their oil is most productive when used with fuels that have low or medium sulfur content.

How often should I change this oil?

It depends on several factors. Semi-synthetic oil usually needs to be changed every 5,000-8,000 miles but if the engine is not new, you might want to change it much more frequently. In any case, it’s always necessary to periodically monitor the oil condition and change it in time.   


Using high-quality engine oil will result in increased productivity of your vehicle and the engine will run much longer without any problems. For this reason, it’s always necessary to choose proven high-quality oils, which use a technological synthetic base and an appropriate set of additives. The oils above are perfect for Duramax engines, providing full protection at extreme loads and temperatures.

Shell Rotella T6 is preferred for commercial use since it provides 100% protection and fuel economy by reducing resistance and providing the smoothest possible friction. As for viscosity, standard 15W-40 will be an optimal all-season version for Duramax. Such oil has great viscosity at 212F and retains its fluidity at -4F.

Frequently asked question

What oil should I use for my Duramax?

The best option for Duramax engines is 15W-40 oils if we’re talking about driving in the medium temperature range. At the highest engine loads, the viscosity of such oil is sufficient to provide the necessary protection and fully coat all the necessary engine parts. Mobil 1 and Delo provide the best solutions in this aspect.

If you drive in a cold climate, 5W-40 oil is the best choice. It should be used in cases when engine operation involves increased oil fluidity during severe cold. In this case, it’s worth paying attention to Rotella options, used not only for car engines but also in industrial and agricultural engines.

What oil does a 6.6 Duramax use?

Duramax engines use synthetic and semi-synthetic diesel oils with additives that help reduce engine wear and achieve considerable fuel economy. Duramax engines are most often filled with 15W-40 oil, versatile in terms of viscosity and operating conditions. The oil works best at high temperatures. For colder climates, you might want to get 5W-40 oil, which allows quick engine start at -22F and maintains the engine well when heated to critical temperatures. Another acceptable versatile option for Duramax engines is 10W-30 oil, which is more fluid but can also be used under certain conditions.

What brand of oil does GM recommend?

First of all, it’s worth saying that GM company has its own oil, recommended for use in many engines – GM Dexos1 5W-40. It’s one of the most versatile options if you’re looking for all-season oil. This oil provides engine protection in all weather conditions. As for third party brands, GM oils are also produced by Mobil 1. For example, Mobil Super 1300 is a great choice for heavy-duty diesel engines, including industrial installations. This oil has many advantages compared to other conventional oils, e.g. a high-quality synthetic base with special additives.

Does GM recommend synthetic oil?

GM most often recommends a combination of traditional mineralized oil and synthetic oil. In fact, such oil effectively protects the engine and helps to save on fuel consumption. Pure synthetic oils are also recommended by the manufacturer since they work longer and can significantly outperform mineralized counterparts in many respects. Synthetic oils are cleaner and provide less friction between engine parts, which has a positive effect on the life span of the engine.

Editorial Staff

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