Best Oil For Duramax 2021 – Buying Guide and Review

If you like trucks, then you’ve no doubt heard of the legendary Duramax engine. Duramax is one of General Motors’ longest-produced engine lines. It’s a family of 6.6-Liter V8 diesel engines that have been made since 2001. GM revolutionized diesel trucks and set a new industry standard with their high-quality Duramax engine. The engine has a number of notable features that set it aside from the archaic, oil-burning diesels of olden days;

  • Improved fuel efficiency. 
  • More horsepower, less engine weight. 
  • Enhanced endurance to high temperatures. 
  • Better cold-starting. 
  • …and more! 

The Duramax is used in most of Chevrolet and GM’s heavy-duty vehicles and is most common in the automakers’ 2500 series of commercial trucks. However, the engine is also used in many of the larger trucks and in several of the work/utility vans produced by the companies. 

While Duramax engines are highly regarded for their enhanced durability and longevity, the best way to ensure that your Duramax lasts as long as possible is to give it the right oil. Motor oil is an essential component to your engine that protects the internal parts from wear and tear, keeps your pistons and cylinders clean, maintains an airtight seal, and improves fuel efficiency and power output. 

In today’s post, we’re going to show you some of the best oil for Duramax engines so that you can keep your Duramax performing like new! 

Best Oil Fur Duramax Engines

GM typically recommends 15W-40 motor oil for their 6.6-Liter Duramax engines. However, in cooler temperatures, the manufacturer states that it’s okay to use a thinner oil like a 5W-40 or a 0W-40. Below, we’ve included a list of our four top oil choices for Duramax engines. 

Good For Extreme Temperature: Shell Rotella T6 Full Synthetic 5W-40 Diesel Engine Oil

Shell’s Rotella line of synthetic oil is widely regarded as one of the top brands on the market. It’s especially good for GM/Chevy Duramax diesels. This full synthetic oil contains added compounds that are designed to provide superior protection from the heavy-duty activities typically performed by these larger trucks. Not only does this mean that Shell Rotella will help you go longer periods of time between oil changes, but it also means that you won’t have to worry as much about over-straining your engine. 

Additionally, this oil features Shell’s patented T6 technology that’s designed to withstand extreme temperatures. This is particularly common on today’s turbo-charged Duramax engines that force extra air into the engine to create higher RPMs and increased combustion. These same properties also make the Shell Rotella a good choice for trucks that spend a lot of time towing on the road. The increased oil strength ensures that the compounds won’t start separating prematurely. 

Another great feature of the Shell Rotella synthetic oil is that it provides better fuel economy when compared to the heavier 15W-40 oil that GM recommends. Since the oil is slightly thinner, it doesn’t give the pistons as much resistance as a thicker oil, which allows the engine to move quicker and smoother with less friction, resulting in more miles per gallon of fuel. As you can imagine, this is especially important with today’s high fuel costs. 

Pros

  • Provides better fuel efficiency than standard 15W-40 Duramax oil. 
  • Rotella T6 patented protection stands up to extreme temperatures. 
  • Advanced synthetic compounds provide great oil stability. 
  • Maintains optimal engine pressure. 

Cons

  • Only works with diesel engines. 

Good For Gas and Diesel Engines: Liqui Moly 2041 Premium 5W-40 Synthetic Motor Oil

If you just have your Duramax diesel engine, then the Shell Rotella discussed above is a great all-around option. However, if you have other heavy-duty work trucks (for example, one of GM/Chevrolet’s gas-powered trucks), then you may prefer to use more versatile motor oil. While the Rotella is only designed for use in diesel engines, LiquiMoly’s 5W-40 synthetic motor oil is designed to be used with both diesel and gas-powered motors. This makes it a better choice for drivers with multiple trucks. 

Admittedly, LiquiMoly is not a very well-known brand in the United States. That is due to the fact that it’s a German brand that has just recently started expanding in the U.S. In Germany, LiquiMoly is regarded as the country’s leader in synthetic blends and designs all of its products to stand up to Germany’s rigorous mechanical quality specifications. 

As a 5W-40, it provides quicker start-up lubrication compared to some of the thicker 15W-40 alternatives on the market. Despite its thinner consistency, though, it still provides excellent resistance to wear and tear, helps to keep your pistons clean, and offers above-average fuel efficacy. 

Pros

  • Made in Germany (where requirements are higher). 
  • Excellent start-up lubrication. 
  • Great choice for most weather conditions. 
  • Works with both diesel and gasoline engines, making it a versatile choice. 

Cons

  • Not as good for extreme temperatures and heavy-duty towing. 

Good For Cold Temperatures: Mobil 1 0W-40 Synthetic Motor Oil

As we mentioned above, GM usually recommends a 15W-40 motor oil for Duramax engines and states that a 5W-40 oil can be used in colder temperatures. However, if you’re dealing with extreme cold, then you may need something even thinner than a 5W-40. If you find yourself constantly driving in sub-zero temperatures, then a 0W-40 could give you the best performance and fuel efficiency for your money. 

Mobil 1 is a global leader when it comes to producing synthetic motor oils. Everybody, from professional racers to professional truckers use Mobil’s products to help their engines stand the test of time. The 0W-40 synthetic oil is a relatively viscous oil that’s also designed to withstand extremely cold temperatures (where a 15W-40 would become thick and may not allow the engine to start smoothly). 

One of the really neat features of this particular synthetic oil is that it’s designed with elastic viscosity. What this means is that, depending on the temperature, the viscosity of the oil can adapt. This makes it a truly versatile fuel that can not only be used in the coldest winters but can also be used in the warmer spring and summer months. 

Pros

  • Trusted by truckers around the world. 
  • Features elastic viscosity to make it a more versatile oil. 
  • Full synthetic oil provides superior protection and engine lubrication. 
  • Performs great in extremely cold temperatures, where thicker oil would reduce efficiency. 

Cons

  • Not as good for heavy towing. 
  • Not great for extremely hot temperatures. 

Good For Heavy-Duty Use: Mobil 1 15W-40 Delvac 1300 Super Motor Oil

While some Duramax owners just use their truck as a daily driver or to tow small trailers and boats, others regularly push the limits of their trucks by towing larger trailers. Many commercial owners also outfit their Duramax vehicles with buckets and other hardware for job sites and various industries. 

While Duramax engines are certainly able to stand up to the challenge of heavy-duty work, they do need special care if you want to preserve the engine’s longevity. This means using a thicker, heavy-duty synthetic oil that’s able to stand up to the higher RPMs, turbo boosts, and sweltering hot temperatures that occur under the hood. 

Mobil 1’s 15W-40 Delvac 1300 Super motor oil is designed to withstand the rigors of heavy-duty towing. Whether you’re towing tractor-trailers or campers across the country, run your own tow rig, or haul heavy concrete in your truck bed, this oil is guaranteed to give you the extra protection that your engine needs. 

It’s a full synthetic that’s specially formulated to work in both low-sulfur and ultra-low-sulfur diesel engines, meaning that it works well with older Duramax engines and the more efficient modern Duramax engines. One of the other great features of this oil is that it contains added cleaning agents that keep pistons firing at optimum efficiency. This, in turn, reduces the emissions and soot produced by your engine. 

Pros

  • Great for older and newer model Duramax engines. 
  • Designed for heavy-duty use. 
  • 15W-40 is recommended by GM for Duramax engines. 
  • Reduced emissions and increased soot control. 

Cons

  • Not good for extremely cold temperatures. 

Choosing The Right Oil For Your Duramax

So, now that you’ve had a chance to look at the best synthetic oils for your Duramax engine, it’s time to go a bit more in-depth. In this section, we’ll take a quick look at some of the top factors to consider when you’re picking out which oil is the best for your Duramax engine. Factors such as the manufacturer’s recommendation, oil viscosity, and your truck’s mileage all play a role when it comes to deciding which is best for you. 

  • Double-Check Your Owner’s Manual

If you’re unsure of what type of oil is best for your particular Duramax vehicle, your best bet is to check your owner’s manual. Duramax engines have been produced since 2001. While the basic design hasn’t changed much in the past two decades, many improvements have been made to create more efficient engines that don’t necessarily need the thick, heavy-duty oil that the older Duramax engines required. 

Another key advantage to using the manufacturer-recommended oil type is that it won’t void your warranty (which is very important when it comes to newer trucks). As long as your following GM’s guidelines to a T, then you can’t be held responsible for any problems that arise with the engine or the rest of the powertrain. 

  • Oil Viscosity

You probably noticed that each of the oils we listed above have different viscosities:

  • 0W-40
  • 5W-40
  • 15W-40

These four-digit codes represent the thickness and winter (W) temperature rating. The lower the number to the left of the “W,” the colder temperatures that the oil can function well under. For example, if you drive in sub-zero climates (Canada, North Dakota, Minnesota, Maine, etc.), then you may benefit from a 5W or even a 0W oil. For warmer driving temperatures, a 15W-40 oil is what GM recommends for Duramax engines

The number on the right side of the dash (-) indicates the relative thickness of the oil. The thickness of the oil is very important as it is specifically designed to keep the engine pressure in check. If you were to use an oil that was too thin, then it could reduce your engine’s vacuum seal, causing engine knocks and increased wear and tear. 

  • Synthetic Vs. Conventional Oil

In most cases, synthetic oil is always a better choice than conventional motor oil. Conventional motor oil is made from crude refined oil. While it’s a decent lubricant, it just isn’t made to stand up to the more extreme temperatures and high-pressure engines produced by most of today’s automakers. 

Synthetic oil is made from 100% synthetic lubricants or is made from modified petroleum or natural gas compounds. It contains added compounds designed to stabilize the oil (keeps it from separating), provides faster lubrication when starting the engine, and even cleaning agents designed to keep your pistons firing clean and powerfully. 

  • High-Mileage Vs. Regular Synthetic

If your Duramax has higher miles, then you may want to consider using a slightly thicker fuel (such as the 15W-40) or using a specially-formulated high-mileage synthetic oil. These options typically have added compounds designed to strengthen your engine seals and prevent leaks and excessive oil burn-off. 

F.A.Q.s

Here are a couple of common questions we’ve received about Duramax engine oil. 

Should I Use Synthetic Oil In My Duramax? 

Yes! Conventional oil just isn’t able to stand up to today’s quality standards and can result in reduced fuel efficiency, less engine power, can burn dirty (produces more soot), and needs to be topped off more often. Conversely, synthetic oil is designed to stand up to long-term use, provides superior protection, and even cleans your engine! 

What Oil Do GM Dealers Use In Duramax Engines? 

GM dealers use their own specially-formulated Dexos 15W-40 synthetic engine oil in Duramax engines. If you take your vehicle into an authorized GM dealer for an oil change, this is what you’ll get. 

What Is Rotella For Duramax? 

Rotella is Shell’s top-of-the-line synthetic oil designed for heavy-duty use. Shell’s Rotella T6 is one of the most commonly used oils by Duramax owners and has a great reputation for quality and versatility. It was the first item on our list above! 

Sources:

  1. https://en.wikipedia.org/wiki/Duramax_V8_engine
  2. https://www.thedieselpage.com/duramax/750kduramaxc.htm
  3. https://www.techenomics.net/2014/02/oil-viscosity-and-its-importance/
  4. https://www.gmdexos.com/about/index.html 

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