7 Best Diesel Motor Oils of 2021

Jerry Wilson
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Are you currently using a diesel motor oil? Is it time to change it? Not sure what one to buy? Looking to seriously improve your diesel engines performance?

If you answered YES to any of these questions, then you’ve come to the right place because we have 7 of the best diesel motor oils available in the market right now. You’ll find a comprehensive rundown of the performance, technical specs, price and more.

Just below, you’ll find the best diesel motor oils of 2021.

NameCategoryProduct
Motul 007250 8100 X-cess 5W-40 Synthetic Gasoline and Diesel Engine OilBest OverallMotul 007250 8100 X-cess 5W-40 Synthetic Gasoline and Diesel Engine Oil
Castrol 03087 EDGE Extended Performance 5W-30 Advanced Full Synthetic Motor OilBudget PickCastrol 03087 EDGE Extended Performance 5W-30 Advanced Full Synthetic Motor Oil
Valvoline 774038 Premium Blue Extreme SAE 5W-40 Full Synthetic Diesel Engine Oil 1 GAUpgrade PickValvoline 774038 Premium Blue Extreme SAE 5W-40 Full Synthetic Diesel Engine Oil 1 GA

1. Motul 007250 8100 X-cess 5W-40 Synthetic Gasoline and Diesel Engine Oil

Our rating: 10 / 10

Motul 007250 8100 X-cess 5W-40 Synthetic Gasoline and Diesel Engine Oil

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Pros:

  • Ideal for high mileage engines
  • Multi-vehicle use
  • Low odor formula

Cons:

  • Very wide range timing intervals
  • Reefer truck advised against

2. Castrol 03087 EDGE Extended Performance 5W-30 Advanced Full Synthetic Motor Oil

Our rating: 9 / 10

Castrol 03087 EDGE Extended Performance 5W-30 Advanced Full Synthetic Motor Oil

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Pros:

  • Great value
  • API SN/GF-4/CF

The Castrol 03087 Oil is a value for money 5-quart pack of Full Synthetic Motor Oil that comes with a Limited Lifetime Warranty for your peace of mind. It has been designed with the latest engineering to provide you with maximum protection while running your engine. Castrol claims that this oil will give your vehicle longer engine life as delivered by API certifications.

This Engine Oil boasts a detergent content of 2%, a viscosity of 5W30, and is suitable for both gasoline and diesel vehicles. The Oil also comes with Castrol Edge 5W-30 technology which is anti-foaming. This captures the chances of oil from going back to the air filter. Also, its special formula provides a protective layer against corrosion.

This Castrol Oil meets the latest industry standards to provide you with top of the line protection and peace of mind.

3. Valvoline 774038 Premium Blue Extreme SAE 5W-40 Full Synthetic Diesel Engine Oil 1 GA

Our rating: 9 / 10

Valvoline 774038 Premium Blue Extreme SAE 5W-40 Full Synthetic Diesel Engine Oil 1 GA

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Pros:

  • Protects against oil breakdown and loss of lubrication
  • Guarantees a clean engine environment
  • Reduces oil consumption
  • Helps protect against deposits and engine sludge
  • Helps prevent premature wear
  • Excellent for cars with turbochargers, supercharged and diesel engines

This is my number one pick since it is the cheapest. It is a mid-grade product—the best of both worlds when it comes to cost vs performance. This is an advanced 4-stroke diesel oil which cuts engine wear and protects against engine sludge. It helps prolong the life of vehicles with turbocharged or supercharger engines. This give this product the competitive edge when it comes to value. This product is better than other engine oils in its price range due to its lubricating ability. It does not let the engine to overheat when it is overloaded and keeps optimal engine temperature. It checks wear and performance decrease resulting from high temperatures. It also protects the engine from seals cracking, valve leaks, and loss of power. It is an ideal product for vehicles with turbocharged or supercharged engines.

4. Royal Purple 04154 15W40 Oil One Gallon

Our rating: 8 / 10

Royal Purple 04154 15W40 Oil One Gallon

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Pros:

  • Cleans effectively
  • Keeps parts lubricated
  • Increases gas mileage
  • 100 percent synthetic

Cons:

  • Might clog sensors
  • Requires frequent filter changes

(12 Pack)

Royal purple’s 04150 oil is one of their most popular, delivering the power you need and the protection you want. This is the standard 0W-40 grade, with all of the options and extreme performance you’d expect from a synthetic blend.

The Royal purple Oil is a great workhorse oil that will be able to keep up with your needs. It’s a full synthetic so you won’t have to worry about contamination, while it still protects your engine or transmission. You can still use this oil to help improve your performance in the long run with the added performance index of 170.

5. Red Line RED21405 15W-40 Diesel Oil

Our rating: 8 / 10

Red Line RED21405 15W-40 Diesel Oil

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Pros:

  • Quality protection in extreme temperatures
  • Exceptional cold weather flow
  • Significant reduction in soot deposits

Cons:

  • Questionable additive package
  • Somewhat hefty price tag for a quart

Red Line has a reputation in the automotive industry for making some of the finest heavy duty motor oils. Their 15W-40 mineral based RED21405 is a step above their other products and features a number of additives such as extra protection in extreme temperatures.

According to the manufacturer, the first synthetic, high quality, and high performance diesel motor oil. The unique additive package allows for consistent flow performance during cold weather and also helps to reduce harmful emissions.

The oil is designed to offer maximum performance and protection in the latest generation of diesel engines. And modern diesel engines can use very high grade of base oils for a high level of lubrication.

6. Mobil 1 120760 Synthetic Motor Oil 0W-40

Our rating: 7 / 10

Mobil 1 120760 Synthetic Motor Oil 0W-40

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Pros:

  • Gets the job done better than the best leading competitors
  • More cost efficient in the future
  • Good protection against wear

Cons:

  • Poor value for money
  • Slight weak against corrosion

Mobil 1 is known for making top-notch motor oils. The 120760 is a good example. As an additive, this oil definitely lives up to Mobil 1’s high standards. The oil is a pretty thick consistency providing good lubrication which makes the oil last a little bit longer.

With that said, I don’t like how they promote wear protection in their ads. Yes, this oil does have extra TBN which is a measure of neutralizing acids which is good. And the ZDDP is quite high at 1600ppm. But once again, this value is far lower than the best performing oils in this category.

And the price of this oil is too high in my opinion. For the price you pay, I would expect a better performing motor oil. And if you look at the life expectancy of this oil, it’s quite low. What’s worse, even if you take into account it’s unbelievable low price, the value isn’t good enough for me to recommend this oil.

7. Shell Rotella T4 Triple Protection Conventional 15W-40 Diesel Engine Oil

Our rating: 7 / 10

Shell Rotella T4 Triple Protection Conventional 15W-40 Diesel Engine Oil

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Pros:

  • Great lubricant and high detergent additive package
  • TAPI & TBN boosting additives
  • Good for VGT & SVGT techs
  • Safety features fit guidelines
  • Good for frequent heavy duty use

Cons:

  • No great viscosity control
  • Not a great choice for extreme high temperature concerns

The Shell Rotella T4 Conventional formula is engineered to meet the needs of modern heavy-duty diesel engines and systems and delivers better fuel efficiency over extended drain intervals.

Rotella T4 Conventional, a part of the Cummins Diesel Oil Advisory Group (CDAG), is a category and performance-leading base oil. It is formulated without a Performance Additive Package for those who want their application or lubricant warranty to only include genuine Cummins diesel additive technology.

Rotella T4 is compatible with all diesel fuels, including biodiesel and demineralized fuel with up to B20. With its high TBN and TAPI to boost fuel efficiency, it keeps heavy-duty engines clean and performs well even in startup and heavy-load conditions.

Frequently Asked Questions (FAQ)

What is the best oil for a diesel engine?

There are several different grades of oil, which differ in terms of performance and price. When you make your selection, you should take a careful look at the owner’s manual to see what your car requires. You may or may not need to purchase oil that is made specifically for diesel engines. Certain tractor trailer rigs, for instance, make their own oil from recycled materials, so they don’t need motor oil at all. Some diesel vehicles can also use regular gas, and they can run on regular motor oil. It turns out that the oil that you purchase simply depends upon what the manufacturer recommends.

Is synthetic oil better for diesel engines?

In short, yes, but you should know a few things up front. Synthetic oil does work better because it is designed to provide superior lubrication to conventional petroleum-based oils. That sounds great, so why does it still come with a caveat?

Have you ever seen a warning on your v8 truck that says….double the miles before an oil change? Yeah, that…s because synthetic is slipperier than conventional oils and it breaks down faster.

This means you will need to change your oil more often.

For most people, this is not a real issue. A few bucks more per oil change is a drop in the bucket when you consider how much money you are saving on gas. It’s also a more than fair trade considering you are getting better gas mileage and better engine protection.

Which diesel engine is the most reliable?

Diesel engines are extremely strong and reliable. A diesel engine, typically, is less economical than regular engines, but there are many benefits of diesel engine over gas engine.

Diesel engines are very efficient and reliable.

Diesel engines require less service or maintenance.

Diesel engines typically hold higher resale values.

In comparison to a gas engine, a diesel engine has the strength to drive the load without any problem. This strength is achieved through the injection of fuel, which produces more power, on diesel combustion. A diesel engine is ideal for off-roading, load driving and pickup trucks, tractors etc.

The diesel engine is also efficient and reliable. The diesel engine is very efficient with nearly 100% of fuel utilised. In contrast, the gas engines are not as efficient and have high fuel loss.

Diesel engines are robust. They can tolerate more load and higher RPMs without giving up.

Can you put 10w30 in a diesel engine?

Yes, you can. However, some manufacturers' specifications for the 7.3L diesel require higher viscosity motor oils. Also, some manufacturers may recommend a different viscosity motor oil, depending on the temperature at which you operate your truck. Thus, even if a higher viscosity motor oil is permissible, it may not be optimal.

Conclusion

The 7 Best Diesel Motor Oils of 2021 article is a cumulative effort by 6 separate pickup truck enthusiasts from throughout the United States. Each contributor has 10 years of experience with diesel trucks and during that time have used just about every major diesel oil manufacturer out there. By the time we were done writing the article together, we had an intellectual resource of knowledge that no manufacturer could ever hope to obtain. The information contained within this article was obtained by extensive driving and testing all of the oils, compiling the raw data into a standard format, and doing massive amounts of analysis. It was the results from all of these combined efforts that landed all of the manufacturers on our recommended list.

Our Recommendation

NameCategoryProduct
Motul 007250 8100 X-cess 5W-40 Synthetic Gasoline and Diesel Engine OilBest OverallMotul 007250 8100 X-cess 5W-40 Synthetic Gasoline and Diesel Engine Oil
Castrol 03087 EDGE Extended Performance 5W-30 Advanced Full Synthetic Motor OilBudget PickCastrol 03087 EDGE Extended Performance 5W-30 Advanced Full Synthetic Motor Oil
Valvoline 774038 Premium Blue Extreme SAE 5W-40 Full Synthetic Diesel Engine Oil 1 GAUpgrade PickValvoline 774038 Premium Blue Extreme SAE 5W-40 Full Synthetic Diesel Engine Oil 1 GA