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The Best Oil for 5.9 Cummins – Top 5 Reviewed

Oil is the lifeblood of your truck’s engine – it’s tasked with reducing friction, cooling, cleaning, sealing, shock dampening, energy transferring and corrosion protection.

Now, even though the 5.9 Cummins likes to mark its territory by leaking oil way too often, it’s still a great engine and should outlive your truck’s frame and body, assuming that you treat it properly with regular oil changes and a good quality synthetic motor oil.

But which engine oil should you use? Is there anything specific that you should look out for when buying diesel engine oil?

Well, stick around because that’s exactly what we’ll be talking about in this article but before we review the five best oils for the 5.9 Cummins, here’s an oil viscosity chart to help you chose the right viscosity for your 5.9 Cummins:


5.9 Cummins Oil Capacity and Oil Viscosity Chart

All 5.9 Cummins versions have a 12-quart oil capacity including the oil filter.

Low ash oil is recommended. Engine oils with high ash content could produce deposits on valves and ultimately lead to guttering and valve burning. The maximum sulfated ash content of 1.85 mass % is recommended for all 5.9 Cummins 12 and 24 valve engines.

Make sure you get the right grade motor oil for your ambient temperature range:

2003 – 2007 5.9L CUMMINS ISB (24 VALVE, COMMON RAIL)

Ambient Temperature RangeRecommended Oil Viscosity
Above 0° FSAE 15W-40
All Temperatures SAE 5W-40 Synthetic

1998.5 – 2002 5.9L CUMMINS ISB (24 VALVE)

Ambient Temperature RangeRecommended Oil Viscosity
Above 10° FSAE 15W-40
10° F to 30° FSAE 10W-30
0° F to -10° F (with block heater)SAE 10W-30
Below 0° F (without block heater)SAE 5W-30 Synthetic

1989 – 1998 5.9L CUMMINS (12 VALVE)

Ambient Temperature RangeRecommended Oil Viscosity
Above 10° FSAE 15W-40
0° F to 10° F SAE 10W-30
0° F to -10° F (with block heater)SAE 10W-30
Below 0° F (without block heater)SAE 5W-30 Synthetic

Note: always consult your vehicles owners manual for the right oil requirements and recommendations.


The 5 Best Oils for 5.9 Cummins


1. Valvoline Premium Blue 8600 ES SAE 15W-40 – Top Pick

Valvoline’s Premium Blue is the engine oil of choice for all Cummins diesel engines as it was developed in partnership with Cummins to provide unrivaled engine protection for their engines.

Lubrication & Protection

When it comes to protection and lubrication for the 5.9 Cummins, Premium Blue is unrivaled by competitors.

The engineers at Valvoline and Cummins worked together to ensure that Cummins engines get the lubrication and protection they need to operate at the highest level. Because of that collaboration, the Premium Blue allows for a 10,000-mile drain extension in Cummins X15 engines and a statistically proven 3% fuel economy improvement potential in Class-8 trucks.

The synthetic base stocks of Premium Blue provide faster and safer starts at freezing temperatures, outstanding cold pumpability, as well as greater resistance to extreme temperatures that the turbocharger in your 5.9 Cummins produces.

Conventional motor oil has pretty poor resistance to heat, therefore it tends to solidify and form deposits inside the turbocharger, mainly. These deposits can fully or partially block the oil feed to the turbo and cause premature turbocharger failure, but the full synthetic Premium Blue resists oil breakdown at extreme temperatures and keeps your turbo lubricated no matter the temperature.

Additive Composition

Valvoline’s full synthetic Premium Blue controls the abrasive soot that your 5.9 Cummins produces and keeps your engine clean thanks to its robust additive package. It uses Dispersive Polymer Technology (DPT) to suppress foaming and inhibit corrosion while protecting the engine’s vital lubrication points from soot related valve train and ring wear.

Compatibility

Like every proper turbo diesel engine oil, the Premium Blue is compatible with modern diesel emissions treatment systems such as Exhaust Gas Recirculation (EGR) and Diesel Particulate Filters (DPF). The 5.9 Cummins, however, does not have a DPF or a traditional EGR valve – those we’re introduced in the 6.7 Cummins in 2007, but it does have a catalytic converted which would most certainly benefit from it and won’t clog up as fast.

The Premium Blue Extreme meets or exceeds the requirements for Cummins CES20086, Volvo VDS-4.5, Mack EOS-4.5, Detroit Diesel 93K222 and Deutz DQC III-10LA.


2. Shell Rotella T6 SAE 15W-40 – Best Value

Shell’s Rotella T6 is hard to beat as it offers the best balance between protection and low price.

Lubrication & Protection

The full synthetic Rotella T6 was designed for heavy-duty diesel engines with maximum protection and extreme heat stability in mind. Being a full synthetic oil, the Rotella T6 is much more stable (less volatile) in extreme heat conditions and is therefore extremely popular and widely used – some people even go as far as filling their motorcycles and high-performance turbocharged gasoline cars with it.

During Noack testing, Rotella T6 15W-40 showed lower volatility when compared to conventional Rotella T4 of the same viscosity index. A low volatility motor oil like the Rotella T6 is very important because volatility affects more than the rate of oil consumption – it directly impacts engine performance, fuel economy, cold temperature starting, and deposit formation.

The Rotella T6 is a huge step up from the semi-synthetic and conventional Rotellas’ when it comes to cold weather performance too, largely thanks to its full synthetic composition. It’s able to quickly reach critical engine lubrication points and it’s exactly what your 5.9 Cummins needs – the first few seconds before the engine builds oil pressure is where most (around 90%) engine wear occurs.

During API industry wear tests, Rotella T6 15W-40 knocked it out of the park as it not only met CK-4 specifications but exceeded them. It demonstrated an 85% improvement in copper corrosion protection and a 98% improvement in lead corrosion protection – and an average of 50% more wear protection than was required for the CK-4 specifications.

Additive Composition

Shell did a great job with their detergent and dispersant package with the Rotella T6 as it provides good oil consumption control. In addition to that, Volvo T-13 test has shown that the Rotella T6 15W-40 has great oxidation resistance and controls acid build up really well – 70% more oxidation protection than required for the API CK-4 certification.

Oxidation control goes hand-in-hand with viscosity control due to the fact that as some lightweight oil molecules “boil-off” and evaporate at extremely high temperatures, the engine oil’s viscosity increases and a thicker, more viscous engine oil makes the engine work harder.

By controlling oil oxidation, Rotella T6 maintains good fuel economy longer throughout the drain interval and maintains cleanliness of the engine.

Compatibility

The Rotella T6 is suitable for almost all modern low emission diesel engines as well as older turbo diesel engines, however, you should always consult your truck’s owner’s manual for engine oil recommendations.


3. Schaeffer Manufacturing Co. SynShield Durability Advantage SAE 15W-40 – Premium Pick

Schaeffer Oil Manufacturing Co. has been in the lubricant business for nearly 200 years and their secret for success is quite simple – they consistently provide lubricants that improve performance, fuel economy, and reliability.

Lubrication & Protection

Obviously, Schaeffer Manufacturing Co. wouldn’t name their oil “Durability Advantage” for no reason – the motor oil exceeds API CK-4 requirements and allows for 85% less wear than conventional CJ-4 engine oils.

The SynShield Durability Advantage uses MicronMoly and Penetro friction modifiers that create a durable and slippery shield between metal-to-metal contact. They reduce wear on the valvetrain, piston rings, bearings, and cylinders while maintaining shear stability throughout the drain interval.

Because it’s a para-synthetic diesel engine oil, the SynShield Durability Advantage has low volatility characteristics and does a great job at controlling oil consumption and preventing oil thickening, which is important for engine performance and fuel economy.

Another benefit of its para-synthetic composition is low temperature pumpability. Because the Durability Advantage 15W-40 quickly flows to the critical lubrication points on cold startups, it minimizes engine wear and reduces the load on the starter, giving you more reliable cold-weather startups.

Additive Composition

The SynShield Durability Advantage has a great additive package that gives the motor oil great cleaning ability and protection against deposits. It’s soot dispersants protect the engine from soot overloading and promote high-temperature piston cleanliness – a 77% better soot control when compared to conventional CJ-4 oils.

Compatibility

The SynShield Durability Advantage 15W-40 is compatible with modern diesel emissions reduction systems such as the EGR, DPF, DOC, and SCR but even though the 5.9 Cummins doesn’t feature them – low ash motor oil is still very useful for the catalytic converter and especially the valvetrain.

It exceeds the requirements for API CK-4, CJ-4; Military specification MIL-PRF2104K; Cummins CES 20081, CES 20086, Ford WSS-M2C171-E, WSS-M2C171-F1 and many more.


4. Royal Purple Duralec Super SAE 15W-40

While the Duralec Super 15W-40 might be pricier than the other diesel motor oils in this list, its price certainly reflects its lubrication, wear protection and overall quality.

Lubrication & Protection

Duralec Super 15W-40 was designed to maximize the life of your heavy-duty turbo diesel engine, while also providing extended drain intervals and improving fuel economy – here’s how:

Because of its synthetic composition, the Duralec Super 15W-40 has great oxidation stability and is able to resist extreme temperatures better than conventional oils of the same viscosity. Unlike conventional oils that evaporate, thicken and form deposits in extreme heat, Duralec Super keeps providing the optimal lubrication that your 5.9 Cummins needs. The combination of low volatility and high oxidation stability is the reason why Duralec Super 15W-40 continues to perform so well even with long drain intervals.

Duralec Super 15W-40 also does a great job at sealing the gaps between your engine’s cylinder walls and piston rings to reduce blow-by, improve combustion efficiency, and to reduce nasty exhaust emissions.  

Additive Composition

It uses an advanced additive package in combination with its synthetic composition to form a tough and durable oil film between metal-to-metal contact, providing outstanding engine wear protection and exceptional cleaning ability.

The additives stick to metal surfaces after shut down and keep them protected from acid corrosion and rust. It’s also engine seal friendly, just like mineral engine oils, so you won’t have to worry about new oil leaks after switching to the synthetic Duralec.

Compatibility

Duralec Super 15W-40 is compatible with other semi-synthetic and mineral motor oils, meaning that you won’t need to flush any little remaining bits of your old motor oil that hasn’t completely drained from the engine – just fill up your engine up with Duralec Super 15W-40 and you’re good to go. Nice and simple.

Lastly, Duralec Super is compatible with most modern diesel emissions control systems – just like you would expect from a premium synthetic diesel motor oil. It meets or exceeds the following manufacturer requirements for Cummins CES 20086, Caterpillar ECF-3, ACEAE9-16, Detroit Diesel DFS 93K222, Volvo VDS-4.5, Mack EO-S-4.5, Renault RLD-4, DeutzDQC 111-1 OLA and MB 228.31. 


5. Mobil 1 Delvac 1300 Super SAE 15W-40

Mobil 1’s Delvac 1300 15W-40 Super meets or exceeds the OEM requirements of quite a few European truck manufacturers, which is saying a lot – Europe has much more strict motor oil requirements.

Lubrication & Protection

Delvac 1300 Super 15W-40 is a high-performance synthetic blend diesel engine oil designed to use in all heavy-duty applications, including marine. It meets or exceeds the requirements for API CK-4 and older, meaning that it’s compatible and recommended for use in diesel engines with the latest emissions control systems and older diesel engines, like the 5.9 Cummins.

Its synthetic composition gives outstanding oxidation stability, meaning that it won’t thicken, form nasty deposits and lose all of its properties as fast as conventional diesel engine oils. It also means that the Delvac 1300 Super 15W-40 is capable of extended oil drain intervals that help the environment and also your wallet since you won’t have to change the oil on your 5.9 Cummins as often.

Delvac 1300 Super 15W-40 stays fluid in cold weather to give your engine smooth starts and immediate protection of your valvetrain, bearings, and other critical lubrication points.

Additive Composition

The special base oil technology with hydro-processed base stocks and an outstanding additive package allows the Delvac 1300 Super 15W-40 to resist excessive oil consumption and corrosive and abrasive wear.

It promotes long gasket and seal life and controls soot buildup really well. Because of its great soot and acid corrosion control additives, the Delvac 1300 Super 15W-40 allows your engine to maintain its fuel efficiency throughout the extended drain intervals.

Compatibility

Delvac 1300 Super 15W-40 was developed in collaboration with the biggest engine manufacturers and is therefore approved for Volvo VDS-4.5 and 4, Renault RLD-3, MB 228.31, Man M 3575, Mack EOS-4.5, Mack EO-O Premium Plus, Deutz DQC II-10 LA, Detroit Fluids Specification 93K218 and 93K222 and meets or exceeds the requirements of Cummins CES 20086 and more.  


Things to Consider Before Buying Engine Oil for the 5.9 Cummins


Even though the 5.9 Cummins is not that picky when it comes to motor oil, there are a few things you should consider before you go out and make your purchase. 

Make Sure You Get the Right Grade (Viscosity) Motor Oil

Viscosity has always been and will continue to be the most important factor when choosing motor oil. It affects heat generation and wear, governs the sealing effect of motor oil, and determines how much energy it will take to start and keep and engine running under various temperature conditions.

Viscosity is a measure of the oil’s resistance to flow and it’s directly affected by the temperature of the oil, where its viscosity decreases with increasing temperature and vise versa. This is one of the reasons why engines are harder to start in freezing temperatures.

To make oil viscosity easier to understand for the buyer, the Society of Automotive Engineers (SAE) developed a scale for motor oil viscosity ratings called oil grade. It’s explained in an easy-to-understand but thorough way by The Repair Specialist in this video:

The engineers at Cummins spent painstaking hours testing different grade motor oils in order to find what works best. They took RPM, clearances between moving parts at different temperatures, and more factors into consideration, therefore it’s extremely important to use the right grade motor oil that they recommend.

Conventional vs Synthetic Oil

There are a number of reasons why synthetic oil is better than conventional but that doesn’t mean that you should only be using synthetic.

Synthetic motor oils have a natural ability to maintain similar viscosity during temperature changes. They don’t thicken as much in freezing temperatures, therefore they perform better in cold temperatures and especially the first seconds after startup where most engine wear actually occurs. Alongside better protection against wear, synthetic oils reduce the amount of energy that is needed to start the engine and keep it running which increases the efficiency of the engine and ultimately gives you better mileage.

And it doesn’t end there – synthetic motor oil kicks conventional oil’s ass in extremely high temperatures as well. One of the main disadvantages of conventional motor oil is its high volatility.

Nowadays, pretty much all diesel engines have a turbocharger which gets really hot under heavy loads and if you shut your engine down and stop the oil flow while the turbo is pretty much red hot, the leftover oil inside the turbo will start boiling. Conventional oil is quite volatile when compared to synthetic, meaning that conventional oil “volatilizes” and “evaporates” easier, leaving deposits that could reduce or completely block oil flow to the turbo – this is called “turbo coking” and it’s something you don’t want to happen to your 5.9 Cummins.

When Should You Use Conventional Oil?

If not specifically recommended or required in your vehicle owner’s manual, using conventional motor oil would make sense if you’re short on cash and your engine isn’t subjected to freezing temperatures, doesn’t have a turbo or is not operating in extreme conditions.

In the owners manual, extreme conditions for the 5.9 Cummins are:

  • Frequent short trips where your engine does not reach the operating temperature of 190° F.
  • Excessive idling (over 10 minutes) at ambient temperatures lower than 32° F.
  • Frequent towing.
  • Dusty driving conditions.
  • Commercial service – taxi, police, delivery, etc.
  • Off-road or desert operation.
  • Extensive operation at high engine RPMs (greater than 2900 RPM) and loads (70% throttle).

However, if your 5.9 Cummins is subjected to these extreme operating conditions or if you don’t mind paying a little bit extra to rightfully preserve its longevity, then full synthetic or semi-synthetic motor oil would certainly be the best choice you can make for your engine.

Low Ash Content

The only requirement apart from the correct viscosity for the 5.9 Cummins is to use low ash engine oil. Engineers at Cummins have noticed in the past that high ash content motor oils would produce deposits on valves to the point where valve burning occurs, therefore Cummins recommends using motor oil that has maximum sulfated ash content of 1.85 mass %. So, as long as you use API CI-4 certified engine oil, you should be good to go. 

Do I Need to Add Oil Additives?

No, you should never use oil additives if you’re running good quality engine oil. Most (if not all) API certified engine oils already have all the additives your engine needs, therefore you would only make the additive ratio too high, which could only harm your engine.

You would only benefit from oil additives if you’re buying the cheapest engine oil possible and don’t change it in time, but even if you would do that, it would almost be cheaper to buy better quality engine oil in the first place. 

Conclusion

The 5.9 Cummins is a reliable engine that isn’t too picky on engine oil, however, that doesn’t mean that you can get away with buying the cheapest stuff you can find – it’s a heavy-duty workhorse after all.

The overall best choice will always be what your truck’s engineers recommend and in this case, it’s Valvoline’s Premium Blue. It’s a synthetic motor oil that has very low volatility and low ash content, which is the most important requirement for the 5.9 Cummins.

But if for some reason you don’t want to use Valvoline’s Premium Blue, any motor oil from this list would work very well too.

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