The 10 Best Diesel Oils -2021 (Review & Guide)

best diesel oil

Wondering which diesel oil is best for your engine?

Knowing which diesel oil is best for your engine is critical if you want your diesel engine to run smoothly and for a long time without causing havoc to your engine.

Our top pick for diesel oils is the Shell Rotella T6 Full Synthetic 5W-40 Diesel Engine Oil.

Diesel engine owners, including those with motorcycles, are extremely happy with its performance. Avid owners rave about how well it works and given how inexpensive it is, it’s a no-brainer making it easy to replace your oil on schedule.

Read the reviews and you’ll get a good feel for how effective this oil is. Whoever thought people could get so passionate about engine oil.

Our Budget Pick is AmazonBasics Full Synthetic Motor Oil. Ya, I never thought I would see the day when I’m including an Amazon label as a top pick. I read the reviews. And then I read the reviews again. With well over 8000 reviews and a rating of 8.6 at the time of publishing, I chose to include it because it didn’t seem right to exclude a product that works well, just because it has Amazon on the bottle.

Our Runner-Up is Royal Purple 04154 15W-40 diesel oil. A great option for diesel engines and those carrying a heavy load. Consumers talk about how it stands the test of the heavy loads and performs better than other diesel oils.

Knowing which diesel oil is best for your engine is critical if you want your diesel engine to run smoothly and for a long time without causing havoc to your engine.


CLICK HERE TO LEARN MORE ABOUT OUR TOP PICK

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IN THIS GUIDE


TOP PICK – Diesel Engine Oil

Shell Rotella T6 Full Synthetic 5W-40 Diesel Engine Oil

What We Like

  • Great for cold and warm environments
  • Prevents sludge and debris build-up
  • Better fuel economy
  • Extends the engine life

What We Don’t Like

  • The oil stinks when burnt

SUMMARY: Shell Rotella has a good reputation for making excellent lubricants for over 40 years. Its T6 full synthetic oil 5W-40 delivers maximum protection to truck or SUV diesel engines.

Engineered with shear stability, T6 5W-40 maintains the optimal pressure in the engine and prevents viscosity loss.

It features multi-functional additives that offer unrivaled protection and keeps the engine clean all the time.

This heavy-duty diesel oil is formulated to prevent wear and tear and works well under cold or high temperatures.

It also comes with anti-oxidation properties that prevent the formation of acids that cause corrosion in your engine.

The only downside of this full synthetic diesel oil is that it has an irritating smell when burnt.


TOP PICK – BUDGET DIESEL OILS

AmazonBasics Full Synthetic 5W-40 Motor Oil

What We Like

  • Excellent for longer drain intervals
  • High resistance to viscosity loss
  • Reduces exhaust emissions
  • Works well in low and high temperatures

What We Don’t Like

  • Poorly designed bottle

Summary: The AmazonBasics Full Synthetic 5W-40 Motor Oil is a high-quality diesel oil formulated to offer better fuel economy in diesel engines.

It’s an ideal oil for longer drain intervals, and it delivers engine protection in high and low temperatures. You won’t have to worry about cold-weather startups.

This fully synthetic oil is highly resistant to viscosity loss and thermal breakdown to ensure optimal pressure in the engine.

Another impressive thing about this diesel oil is that it’s compatible with both new and old engines.

The AmazonBasics Full Synthetic 5W-40 Motor Oil also includes beneficial additives that keep the engine clean by preventing sludge and deposit accumulation in the engine.


RUNNER-UP BEST DIESEL OILS

Royal Purple 04154 15W 40 Diesel Engine Oil

What We Like

  • Prevents corrosion
  • Makes the engine run smoother
  • Great additives
  • Compatible with conventional and synthetic blends

What We Don’t Like

  • The can lacks markings

Summary: If you are looking for an easy way to upgrade to a higher quality full synthetic diesel oil, you can’t go wrong with the Royal Purple 04154 15W-40 diesel oil.

It combines patented additives and premium base oils that make it a more efficient diesel oil and its ZDDP additives help optimize the emissions catalyst system.

This API licensed motor oil prevents debris build-up and eliminates all sludge and deposits to keep your engine clean and run smoothly.

The best thing about this diesel oil is that it’s compatible with conventional and synthetic blend oils.

It’s recommended that you change the Royal Purple 04154 15W-40 after driving 3,000 to 5000 kilometers.


TOP 10 BEST DIESEL OILS

TOP PICK – Diesel Engine Oil

Shell Rotella T6 Full Synthetic 5W-40 Diesel Engine Oil

What We Like

  • Great for cold and warm environments
  • Prevents sludge and debris build-up
  • Better fuel economy
  • Extends the engine life

What We Don’t Like

  • The oil stinks when burnt

SUMMARY: Shell Rotella has a good reputation for making excellent lubricants for over 40 years. Its T6 full synthetic oil 5W-40 delivers maximum protection to truck or SUV diesel engines.

Engineered with shear stability, T6 5W-40 maintains the optimal pressure in the engine and prevents viscosity loss.

It features multi-functional additives that offer unrivaled protection and keeps the engine clean all the time.

This heavy-duty diesel oil is formulated to prevent wear and tear and works well under cold or high temperatures.

It also comes with anti-oxidation properties that prevent the formation of acids that cause corrosion in your engine.

The only downside of this full synthetic diesel oil is that it has an irritating smell when burnt.


TOP PICK – BUDGET DIESEL OILS

AmazonBasics Full Synthetic 5W-40 Motor Oil

What We Like

  • Excellent for longer drain intervals
  • High resistance to viscosity loss
  • Reduces exhaust emissions
  • Works well in low and high temperatures

What We Don’t Like

  • Poorly designed bottle

Summary: The AmazonBasics Full Synthetic 5W-40 Motor Oil is a high-quality diesel oil formulated to offer better fuel economy in diesel engines.

It’s an ideal oil for longer drain intervals, and it delivers engine protection in high and low temperatures. You won’t have to worry about cold-weather startups.

This fully synthetic oil is highly resistant to viscosity loss and thermal breakdown to ensure optimal pressure in the engine.

Another impressive thing about this diesel oil is that it’s compatible with both new and old engines.

The AmazonBasics Full Synthetic 5W-40 Motor Oil also includes beneficial additives that keep the engine clean by preventing sludge and deposit accumulation in the engine.


RUNNER-UP BEST DIESEL OILS

Royal Purple 04154 15W 40 Diesel Engine Oil

What We Like

  • Prevents corrosion
  • Makes the engine run smoother
  • Great additives
  • Compatible with conventional and synthetic blends

What We Don’t Like

  • The can lacks markings

Summary: If you are looking for an easy way to upgrade to a higher quality full synthetic diesel oil, you can’t go wrong with the Royal Purple 04154 15W-40 diesel oil.

It combines patented additives and premium base oils that make it a more efficient diesel oil and its ZDDP additives help optimize the emissions catalyst system.

This API licensed motor oil prevents debris build-up and eliminates all sludge and deposits to keep your engine clean and run smoothly.

The best thing about this diesel oil is that it’s compatible with conventional and synthetic blend oils.

It’s recommended that you change the Royal Purple 04154 15W-40 after driving 3,000 to 5000 kilometers.


Valvoline 774038 Premium SAE 5W-40 Full Synthetic Oil

What We Like

  • Outstanding oxidation resistance
  • Superior wear protection
  • Great for all weather conditions
  • Keeps the engine clean

What We Don’t Like

  • The handle could be better

Summary: The Valvoline 774038 Premium SAE 5W-40 is an efficient oil formulated to provide optimal performance for your engine in cold and hot conditions.

It keeps your heavy-duty diesel engine well-lubricated to prevent wear and extend its lifespan.

Packed with synthetic base stocks, it ensures fast and safe engine starts even when extremely low.

The diesel oil also doesn’t get too thin when operating under high temperatures or pressure.

Unlike most conventional oils, Valvoline 774038 Premium SAE 5W-40 collects and eliminates all the deposits and sludge to keep the engine clean and healthy.

When you fill your oil tank, it will last long to ensure that you stay on the road and reduce your trips to the mechanic.


Shell Rotella 550050467 T6 Full Synthetic 15W-40 Diesel Engine Oil

What We Like

  • Improves fuel economy
  • Resists viscosity loss
  • Excellent additives
  • Reduces sludge formation

What We Don’t Like

  • The lubricating property doesn’t last long

Summary: The Shell Rotella T6 Full Synthetic 15W-40 is a heavy-duty engine oil formulated with a Triple Protection Technology.

It’s designed to keep up with varied driving conditions and engine requirements for modern low emission. It also works great in older working diesel engines.

The Shell Rotella T6 Full Synthetic 15W-40 features additives that protect the engine from wear and removes all deposits for smooth running.

This oil resists break down when operating in high temperatures and pressure to protect the engine all the time.

Most drivers who use this oxidation-resistant diesel oil reveal that it delivers up to 50% increased mileage and optimal engine performance.

However, some users claim that the lubricating factor in this oil doesn’t last long.


Mobil 1 120782 5W-40 Synthetic Motor Oil

What We Like

  • Improves fuel economy
  • Resists viscosity loss
  • Reduces service intervals
  • Protects the engine from wear

What We Don’t Like

  • Gallon design could be better

Summary: The Mobil 1 120782 5W-40 Synthetic Motor Oil features advanced viscometric and formulations that improve your vehicle’s fuel economy.

It’s designed to lubricate diesel engines and prevent wear to extend the engine life.

With various additives like cleaning agents, the Mobil 1 120782 5W-40 Synthetic Motor Oil keeps your engine clean by preventing sludge build-up in high temperatures.

This diesel oil works well in both cold and hot conditions to protect the engine and improve its overall performance.  

It lowers the overall cost of running and maintaining your vehicle and also enhances its efficiency.

The only drawback of this diesel oil is its gallon is not practical for easy pouring.


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

What We Like

  • Formulated for shear stability
  • Offers great engine protection
  • Ideal for old and new engines
  • Keeps the engine cleaner
  • Prevents oxidation

What We Don’t Like

  • Irritating smell when the oil is burnt

Summary: The Shell Rotella T4 15W-40 is an outstanding diesel oil formulated for improved protection and keeping diesel engines cleaner throughout the oil drain interval.  

It features an exclusive low ash formulation that protects the exhaust catalysts and filters in the latest low emission vehicles.

This diesel oil meets API CJ-4 requirements and is made to deliver extra performance in new and older vehicles.

It’s also formulated for shear stability performance to prevent viscosity loss and maintain optimal pressure in the engine.

Unfortunately, the oil may produce an irritating smell when burnt.


Motul 8100 X-Clean EFE 5W-30 Fully Synthetic Oil

What We Like

  • Extends engine life
  • Better fuel economy
  • Prevents debris and sludge build-up

What We Don’t Like

  • The container nozzle is hard to pull out

Summary: Motul is an excellent brand recognized worldwide for the quality synthetic lubricants they have produced for over 160 years. One of their top-rated products is the Motul 8100 X-Clean EFE 5W-30.

The Motul 8100 X-Clean EFE 5W-30 is a 100% synthetic oil designed to provide high protection and better fuel economy.

It features synthetic base stocks combined with friction modifier molecules to deliver excellent performance in your vehicle’s engine. This oil is specially designed for the latest generation vehicles.

With high lubricating properties, Motul 8100 X-Clean EFE 5W-30 reduces friction in the engines and resists wear and tear.

It functions well under cold and high temperatures by resisting viscosity loss to maintain maximum engine pressure.


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

What We Like

  • Outstanding oxidation resistance
  • Extends the engine’s life
  • Excellent additives and properties
  • Superior engine protection

What We Don’t Like

  • The seal under the cap is weak and can lead to leaks.

Summary: According to Valvoline, Valvoline Premium Blue is the only oil recommended and endorsed by Cummins®.

It’s designed to provide lubrication and protection to your heavy-duty diesel-engine oil and performance and protection in modern, emissions treatment equipped diesel engines, including those with Exhaust Gas Recirculation (EGR) and Diesel Particulate Filters (DPF)

This oil has superior base stocks that facilitate a safe and fast start to your engine even after staying overnight under extremely cold temperatures.

It provides maximum protection to heavy-duty diesel engine vehicles, trucks, and tractors. The performance is consistent with both on-road and off-road applications.

This oil lasts long, even under extreme working conditions. It also has a unique 10,000-mile drain extension and can last 60,000 miles if used with a fuel efficiency of equal or more than 6.5mpg.


Mobil Super 112786 15W-40 Delvac 1300 Motor Oil

What We Like

  • Affordable
  • Reduced low-temperature sludge build-up and high-temperature deposits
  • Excellent at dealing with low-temperature sludge control
  • Good service for an extended period

What We Don’t Like

  • Not usable in all car brands

Summary: Mobil is a prominent name in the automobile industry, and with all the years they have lasted in the market, you are sure the oil will give exceptional protection to your vehicle.

This oil is formulated specially to give great control over low-temperature sludge in stop-and-go service and superior control of oxidation and high-temperature deposits.

It provides extra high performance and extends your vehicle’s engine’s life even in off-road applications and in all-weather conditions.

The Mobil Super 112786 15W-40 Delvac 1300 Motor Oil can last up to 30,000 miles before requiring a drain. It will save you a lot of time and money you would spend on frequent trips to the pump.

Fully backwards compatible, Mobil Delvac 1300 Super will also deliver the same exceptional performance in older conventional engines. As a result, they exceed the API CJ-4, CI-4 PLUS and CH-4 service categories as well as key Original Equipment Manufacture (OEM) requirements for 2007 engines.


Liqui Moly (2040-12PK Premium 5W-40 Synthetic Motor Oil

What We Like

  • Works well with diesel and gas engines
  • Energy conserving (fuel economy) SAE 5W-40 motor oil for the latest engine concepts such as multi-valve arrangements, variable cam and timing configurations, turbocharging, supercharging, inter-cooling
  • Provides instant lubrication after a cold start
  • Good for extended oil change intervals and highest demands

What We Don’t Like

  • Not usable in all car brands

Summary:

Summary: Liqui Moly’s German-made synthetic oil works in gas and diesel engines. It’s fully synthetic, energy-conserving (fuel economy) SAE 5W-40 motor oil for the latest engine concepts (both gas and diesel), such as multi-valve arrangements, variable cam and timing configurations, turbocharging, supercharging, inter-cooling, etc.

Not only does it provide instant lubrication after a cold start but it is also good if you aren’t changing your oil at regular intervals so what makes this a particularly good oil is that you can run your car longer without an oil change. So, if you don’t change the oil on-time, you won’t need to be too concerned about damaging your engine.


4 Benefits of Diesel Oil

1.Improve Fuel Mileage

Using the best diesel oil in your vehicle will make your engine run smoothly and efficiently.

This will increase your vehicle’s fuel diesel mileage to ensure that you spend more time driving and less time and money at the pump.

2. Extend Engine Life

Diesel oil comes with a higher degree of natural solvency, which means that it can clean and eliminate deposits.

It will remove the sludge and gunk from your motor to ensure that it runs smoothly. This will extend your engine life and protect the components that make up the engine.  

3. Maximize Engine Performance

Diesel oil is formulated to enhance your engine’s power, especially for hauling heavy loads and trailers.

It allows the engine to run smoothly with high power by removing debris and blocking gunk.

4. Minimize Oil Changes

Diesel oil is also crucial for increasing the time between your next oil change, depending on the type of vehicle and motor oil used. This means that you will reduce the amount of money and time you spend while changing the oil.


Types of Diesel Oil

Full Synthetic

Full synthetic motor oil features a complex and unique molecular structure. It comes with additives and properties for optimal engine protection and top-notch performance for your engine.

Unlike conventional oils, synthetic oil is not made from crude oil, so it’s formulated with zero impurities are common in synthetic oils.

Most synthetic oil brands use a patented blend of anti-corrosion and cleaning additives to enhance your engine’s life.

Synthetic Blend

Synthetic blend diesel motor oil is usually a mixture of conventional oils and brands of synthetic base oil.

They contain conventional oils and some synthetic compounds to improve their efficiency and protect the vehicle’s engine.


5 Things to Consider When Choosing a Diesel Oil

1.Viscosity

It’s essential to consider the manufacturer’s viscosity grade when buying the best diesel motor oil.

Diesel engines are usually rated between 15W 40 and 5W 40, in which the number before W represents the thickness or oil when cold. The number after W indicates oil thickness under average temperatures.  

The best diesel motor oil should deliver optimal engine performance even when under pressure.

2.Additives

Different diesel motor oil brands have a diverse patented blend of additives to improve specific oil properties.

Additives like viscosity-index improvers ensure that the oil doesn’t become too thin when operating at higher temperatures. Other additives like cleaning detergents ensure that the engine remains clean.

It’s essential to determine which additives will work best for your engine and then go for the diesel motor oil that has them.

3.Compatibility

When buying the best diesel oil, it’s vital to determine if the oil is compatible with your vehicle’s existing oil.

If you opt to buy oil that is not compatible, you will have to drain the existing oil before pouring it into the tank.

It’s also essential to confirm from the user manual when you are not sure of what oil works best for your vehicle.

4.Price

Your budget is also very crucial when it comes to choosing the best diesel motor oil. Synthetic blends and conventional oils are usually cheap as you can get them under $20.

Full synthetic oils are a bit expensive and they vary in price, depending on brand and quality. They are best if you are looking for unmatched engine protection and efficiency.

However, if you just want to enjoy some benefits of full synthetic oils without spending a lot of money, synthetic blends will be okay.

5.Type of Driving

The best diesel oil also depends on your driving patterns. If you drive a vehicle that carries heavy loads, you will want to use higher quality synthetic oil for the best results.


FAQs For The Best Diesel Oils

Is Synthetic Oil Better for Diesel Engines?

Yes, synthetic oil is better for diesel engines as it can withstand high temperatures and extreme pressures.

Because diesel engines produce more power and generate a lot of heat due to their high-performance nature, they need an oil brand that can deliver optimal protection in extreme temperatures and pressures.

Conventional oils lack any additives as they are made by refining oils and they cannot offer the required protection to diesel engines. If you use conventional oils in your diesel engine, the oil will disintegrate quickly as they can’t withstand high temperatures and extreme pressures.  

The best thing to do is to use synthetic oils in your diesel engine as they can withstand extreme temperature and pressure and they have additives and properties to protect your engine all the time.

What Happens When You Put Regular Oil in a Diesel Engine?

If you put regular oil in your diesel engine, it disintegrates as it cannot withstand high temperatures and pressure. This means that it won’t offer the required lubrication and leaves your engine exposed to friction and wear, which will shorten its lifespan.

What is the Best Oil to Use in a Diesel Engine?

The best oil to use in a diesel engine is full synthetic as it is efficient and delivers great protection for the engine.

A lot of research is done when formulating these oils, and it increases the production cost.

However, the high cost for fully synthetic oil is worth it as it comes with more additives that make it more efficient and some of these additives include cleaning agents to keep your engine clean and healthy. They work by preventing the formation of sludge and removing all deposits.

Synthetic oil is also resistant to oxidation and prevents the formation of acids in the engine. This inhibits corrosion of the various engine parts, guaranteeing a long lifespan.  


Summary – The Best Diesel Oil

Knowing which diesel oil is best for your engine is critical if you want your diesel engine to run smoothly and for a long time without causing havoc to your engine.

If you’re still having difficulty making a decision, here’s a quick summary of our findingd:

Our top pick for diesel oils is the Shell Rotella T6 Full Synthetic 5W-40 Diesel Engine Oil.

Diesel engine owners, including those with motorcycles, are extremely happy with its performance. Avid owners rave about how well it works and given how inexpensive it is, it’s a no-brainer to replace the oil on schedule.

Read the reviews and you’ll get a good feel for how effective this oil is. Whoever thought people could get so passionate about engine oil.

Our Budget Pick is AmazonBasics Full Synthetic Motor Oil. Ya, I never thought I would see the day when I’m including an Amazon label as a top pick. I read the reviews. And then I read the reviews again. With well over 8000 reviews and a rating of 8.6 at the time of publishing, I chose to include it because it didn’t seem right to exclude a product that works well, just because it has Amazon on the bottle.

Our Runner-Up is Royal Purple 04154 15W-40 diesel oil. A great option for diesel engines and those carrying a heavy load. Consumers talk about how it stands the test of the heavy loads and performs better than other diesel oils.

We hope that this review and buyer’s guide has helped you determine which diesel oil will work best with your engine.


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Last update on 2021-04-10 / Affiliate links / Images from Amazon Product Advertising API