Are you a truck owner who is currently searching for the best oil for diesel engines that will help maximize your pickup’s longevity?
If so, you are in the right place!
In this PopularMechanic.com guide, you will learn:
- What is Diesel Engine Oil?
- How Does Diesel Engine Oil Work?
- What are the Different Types of Diesel Engine Oil?
And More!
Below is a quick list of all our top products. Keep scrolling to learn more about how to choose the best oil for diesel engines.
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Our Top Pick
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Our Top Pick
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Royal Purple 04154 15W40 Oil
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View on Amazon |
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Best Budget
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Best Budget
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Mobil 1 120760 Synthetic Motor Oil 0W-40
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View on Amazon |
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Best High End
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Best High End
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Castrol 03849 GTX Diesel 15W-40 Motor Oil
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View on Amazon |
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Shell Rotella T4 Triple Protection Conventional 15W-40 Diesel Engine Oil
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View on Amazon | |
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Motul 007250 8100 X-cess 5W-40 Synthetic Gasoline and Diesel Engine Oil
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View on Amazon |
Our Overall #1 Rated Pick
(updated 6/24/2020)
Top Overall Pick:
Our overall #1 pick for the best oil for diesel engines is Royal Purple 15W-40 Synthetic Oil.
Royal Purple 15W-40 Synthetic Oil is specifically engineered to meet the strenuous demands faced by a diesel engine.
Royal Purple aids in fuel efficiency, and also prolongs the service life of many emissions based components, which is typically a weak spot of many modern diesel engines.
This oil also includes a comprehensive anti-wear additive package that attacks corrosion at its source.
If you are looking for the best diesel oil to keep your truck’s engine running for years to come, be sure to check out Royal Purple Synthetic 15W-40
We have just the information you need to keep your heavy-duty truck running in a reliable fashion for years to come.
In order for your diesel truck to work as hard as you do, it must be maintained to a high degree.
This begins with servicing your truck as specified, using only the best in diesel motor oil when conducting oil changes.
What follows is a comprehensive guide to selecting the best oil for the job at hand, and maximizing diesel engine performance, while minimizing engine wear.
Top 5 Best Engine Oils For Diesel Vehicles
What Is Diesel Engine Oil?
Oil that is used in internal combustion engines, whether a diesel or gasoline engine, provides lubrication to internal components. This minimizes wear, and increases engine life.
This is done by cutting down on metal-to-metal friction. Friction within an engine is always a bad thing.
As two metal surfaces rub together, their surfaces are eroded and heat is produced.
This metal erosion inhibits engine performance and can lead to catastrophic failure if bearings, camshaft lobes, or cylinder walls become damaged.
Heat is also dissipated in part, as friction is minimized, this aids in the prevention of overheating and the myriad of troublesome issues that comes with it.
In a diesel engine, oil performs several additional functions outside of providing engine protection.
In turbo diesel engines, engine oil is supplied to a turbocharger, thereby keeping it lubricated. This prevents bearings from being damaged, and the turbo from ultimately locking up.
In HEUI (Hydraulic Electronic Unit Injector) Diesel engines, oil is used to provide the needed hydraulic force to fire the engine’s injectors.
In these engines, injectors are actuated both electric and hydraulic. Engine oil that is dirty, broken down, or of poor quality can lead to injector operation issues such as stiction.
One of the most common HEUI diesel engines found in pick-ups is the enormously popular 7.3 liter Powerstroke, used in Heavy-Duty Series Ford trucks for a number of years.
To learn more about the HEUI diesel system, check out this article.
Viscosity Grades
Diesel oil is offered in a number of different viscosities, with each carrying its own designation as to its properties. Some of the most popular viscosities of diesel oil are SAE 15W-40 and SAE 5W-40.
Oil viscosities are denoted by their SAE (Society of Automotive Engineers) ratings. In these ratings, numerical values are given to dictate resistance encountered by engine oil at certain temperatures.
The first number in this rating refers to an oil's cold viscosity, while the latter refers to an oil's viscosity when warm.
For example, 15W-40 diesel oil has a cold-weather viscosity of SAE 15 when cold, and SAE 40 when warm.
The viscosity of oil that a particular engine manufacturer calls for can be found in a truck’s owner’s manual, or on the oil fill cap of most engines.
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How Does Diesel Engine Oil Work?
Diesel Engine oil essentially lubricates all moving internal engine components.
These components are allowed to reciprocate and move across one another in a lubricated fashion, as opposed to in the form of metal to metal contact.
This protects the individual engine parts from premature wear and failure, which is immensely important, as heavy-duty engines of the diesel variety are typically designed to offer an extended service life.
Diesel oil begins its journey in the oil pan, where the majority of the engine’s capacity of oil resides when at rest.
A pick-up draws this oil from the pan through force generated by the engine’s mechanical oil pump.
This pump is operated when the engine is running, and allows fuel to be circulated about the engine in the desired quantities based upon engine load.
Prior to being distributed throughout the engine, oil travels through the oil filter.
The oil filter strains the oil of any impurities and metal shavings, preventing any downstream contamination.
From there, both the top-end (cylinder heads) and bottom end (engine block), as well as all of their associated components are supplied with fresh engine oil.
This oil then drains back to the oil pan through a series of channels, where it once again begins its journey.
Diesel Oil Properties
All diesel oils consist of base oil, as well as various additive packages that include detergents, dispersants, friction modifiers, and viscosity index improvers.
This additive technology enhances shear stability, provides additional wear protection, and stabilizes overall composition for minimization of oil consumption.
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What Are The Different Types Of Diesel Engine Oil?
Diesel oil comes in several different varieties.
Much of the difference in these varieties can be found in the various base stock used in these oils.
The most common types of diesel oil are fully synthetic, synthetic blend, high mileage, and conventional oils.
Conventional Oil
Conventional motor oil consists of a basic, refined petroleum type base stock, that is fortified with additives such as detergent packages to prevent deposits and other forms of build-up.
In most cases, conventional oil is the least expensive variety of motor oil, yet is still highly effective in most vehicles and driving scenarios.
However, those who prefer the use of conventional oil must stay on top of oil change intervals, as this oil type does not resist breakdown as well as synthetic alternatives.
High Mileage Oil
High mileage motor oils can differ substantially in their composition. However, the overall goal of these oils are to provide your aging engine with added protection, in order to keep it running strong well into its twilight years.
In many cases, high mileage variants consist of a conventional oil base with specialized additives.
Alternatively, a number of high mileage products actually consist of a synthetic blend oil, that provides a mix between conventional and synthetic oil technologies.
Synthetic Blends
Synthetic blend and high mileage motor oils often overlap in at least some regards.
Synthetic blend oils primarily consist of conventional base stock, with a certain degree of synthetic oil added to the mix.
The exact amount of synthetic oil added to the blend varies from one product to the next.
However, synthetic blends typically contain enough synthetic oil to extend service intervals and exhibit additional anti-wear capabilities, even under extended periods of high-performance demands.
Synthetic Oil
Synthetic engine oil is engineered to outlast and outperform conventional motor oil, in almost any circumstance.
Full synthetic oil is also known for its ability to withstand high demand driving conditions and resists breakdown.
In many cases, the time between oil change intervals is extended when synthetic oil is used, due to its overall resilience and longevity.
While synthetic motor oil is undoubtedly the most expensive of all oil types, this price difference is typically offset by a less frequent maintenance schedule.
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What To Look For In Oil For Diesel Engines
Before making any purchase, there are a number of factors that should be considered when attempting to locate the best diesel engine oil for high-quality protection. By giving these factors due consideration, you will ensure that you purchase only a product that protects your diesel engine from start-up to shut down, and in all weather conditions.
Correct Viscosity Grade
Prior to beginning your search, it is important to figure out which viscosity of oil your engine calls for.
The bulk of diesel engines on the road today call for 15W-40 or 5W-40 viscosity oil, though other alternatives do exist.
Look carefully at your truck’s owner’s manual for the viscosity grade that is called for.
In the absence of an owner’s manual, most engine oil fill caps will have the required viscosity printed on their up-facing surface.
Care should be taken to only use the correct oil that is specified for your vehicle.
Many manufacturers will deny warranty claims related to premature engine malfunction and wear if oil outside of that specified is used.
Additionally, particular motor oils are specified for use based upon their ability to enhance fuel efficiency and aid in adherence to the latest emissions standards.
Additives
Diesel oil is prone to contamination from byproducts of the combustion process. Therefore, quality diesel oils feature a number of detergents that assist in maintaining oil integrity.
These detergents also prevent the build-up of deposits within the engine that can lead to performance-related issues down the road.
Detergents also lessen the chance of sludge build-up within aging diesel engines.
Additional additives typically include anti-wear agents, corrosion inhibitors, and viscosity-index improvers.
Most oil manufacturers list the general contents of their additive packages on their web pages.
This information can be accessed to compare one particular brand to the next in a bid to determine which oil will provide the best protection for your truck’s engine.
Certificate Of Quality
When considering which diesel oil to purchase, it is advisable to only consider products that feature the API (American Petroleum Institute) seal on their packaging.
This seal is issued to products that have been evaluated by a third-party governing body, and have been shown to meet industry standards.
The API evaluates various engine oils on their ability to meet standards set forth by the International Lubricant Specification Advisory Committee.
This oversight serves a vital role in providing consumers with a firm understanding of which oils will provide their vehicles with the highest level of protection.
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Top 5 Best Oil For Diesel Engines (2020 Review)
Pick #1: Royal Purple 04154 15W40 Oil
While not likely as well known by many as some of the other names found on this list, Royal Purple has been coming on strong for quite some time in the oil manufacturing business, with a specialized emphasis on synthetic products.
In fact, Royal Purple carries much fanfare from those involved in high-performance functions.
Royal Purple boasts of its high-performance engine oil’s increased capacity to enhance fuel efficiency and prolong emissions component longevity.
This oil also includes a comprehensive anti-wear additive package that attacks corrosion at its source.
The list of additives included in Royal Purple allow you to unlock the true potential and longevity of your truck’s diesel engine.
Pros
Cons
Mobil 1 has been a pioneer of synthetic motor oil technology for many years and has been on the leading edge of numerous breakthroughs in that realm.
This has positioned the company as a perennial powerhouse within the synthetic oil market.
This reputation for excellence has also carried over into the diesel engine oil market as of late.
Mobil 1 Synthetic 0W-40 is specifically engineered to meet the high-performance demands of today’s modern diesel engines.
This oil is well suited to use with turbocharged and direct injection diesel engines.
You can also count on Mobil 1 Synthetic 0W-40 to extend the life of your engine, with its proprietary blend of anti-wear additives.
As a result, your truck will run longer and far more efficiently than you ever likely thought possible.
Pros
Cons
Castrol is another name within the oil manufacturing industry that carries substantial weight.
Castrol has built quite the reputation for developing only products which meet the most stringent of quality demands.
In recent years, Castrol has poised itself as a leader in the diesel engine oil sector of the market as well.
Castrol GTX 15W-40 Diesel Oil is specifically engineered for use in vehicles that operate under severe service conditions.
The additive package included in this oil ensures that a film of oil is adhered to all engine components.
This assures that no preventable metal to metal contact takes place, thereby extending the service of your engine.
At the same time, purpose specific detergents clean internal surfaces.
Pros
Cons
For decades, Shell Rotella has been the gold standard of diesel oil, with likely more gallons sold than any other diesel oil on the market.
This legacy of excellence doesn’t appear to be coming to an end anytime soon, as now, just as much ever, Shell Rotella is flying off of automotive parts shelves everywhere.
Shell Rotella T4 15W-40 offers next-level protection for your diesel engine through the use of an advanced additive package.
This package includes anti-wear agents, detergents, and oxidation inhibitors.
The sum of these additives provides both new and older diesel engines with a high degree of protection, while simultaneously cleaning performance impeding deposits.
Pros
Cons
Motul is a brand that, while somewhat unfamiliar to those of us in American, is enormously popular in the foreign high-performance market.
This brand is actually one of the top producers of synthetic oil worldwide and caters to vehicles that find themselves in the most demanding of circumstances.
Motul X-cess 5W-40 Synthetic Diesel oil is known for its ultimate level of protection that is highly resistant to premature breakdown.
This oil also features high temperature, high shear stability and very low volatility.
This means that Motul will have you covered even when putting your truck up against the most extreme of circumstances.
Pros
Cons
Our Top Pick: Royal Purple 04154 15W40 Oil
My top pick for the best oil for diesel engines is Royal Purple 15W-40 Synthetic Oil.
This oil is specifically engineered to meet the strenuous demands faced by a diesel engine.
Royal Purple aids in fuel efficiency, and also prolongs the service life of many emissions based components, which is typically a weak spot of many modern diesel engines.
Royal Purple also contains a number of additives that cleans your engine’s internal components while it is in service.
These same additives also ward off the onset of corrosion, which is a death sentence to internal engine bearings.
This results in an engine that maintains a high level of efficiency, no matter how many years or miles you put in the rearview mirror.
If you are looking for the best diesel oil to keep your truck’s engine running for years to come, be sure to check out Royal Purple Synthetic 15W-40.
Plus, it's an excellent value for the money! Check the low price now on Amazon.
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