The Best Oils for 6.7 Cummins: Keep Your Engine Running Smoothly

Keep your engine running at peak efficiency with our picks for the best oil for Cummins engines.

byCorrina Murdoch| UPDATED Jan 26, 2022 2:38 PM
The Best Oils for 6.7 Cummins: Keep Your Engine Running Smoothly

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BYCorrina Murdoch/ LAST UPDATED ON January 26, 2022

If you drive a Dodge RAM, whether it’s a 2500 or a 3500 pickup, you know the thrill of the sheer power it supplies. These engines have a proud history dating back to 1919, when Rudolf Diesel partnered with William Cummins — that’s right, the inventor of diesel and founder of Cummins motors have intertwined stories. Literally first to market, this Indiana-based company took the industry by storm. It also offered the brand a leg-up on innovation, enabling them to advance the technology, refine the parts, and craft fluids meant to truly optimize their engines. Cummins are prevalent in Dodges, with the 6.7 boasting up to 400 horsepower and impressive torque. Of course, to access this ability, the engine relies on maintenance and lubrication. Finding the best oil for 6.7 Cummins engines is about more than optimizing efficiency, it’s about keeping your ride healthy for longer, too. To lend a hand, we’ve hunted down the best oil for 6.7 Cummins rides to keep your vehicle in fighting form.

Best Overall
Quaker State 10W40 Protective Oil

Quaker State 10W40 Protective Oil

Coming in a 5-gallon container, this heavy-duty diesel oil is meant to prolong engine life. Ideal for high-mileage vehicles, it creates a cleaner burn and added fuel efficiency.
  • Best for cars with more than 75,000 miles
  • Includes seal conditioners
  • Prevents leaks and slows oil consumption process
  • Spout requires a funnel for smoother pours
  • Conditioner may be harsh on newer Cummins engines
Best Value

Cummins Onan 15W40 Oil

Made specifically for this purpose, this 15W40 oil comes in a single quart. It’s priced affordably and you can rest easy knowing it’s a match for your 6.7 Cummins.
  • Limits consumption of oil
  • Retains integrity at high temperature
  • Reduces risk of oxidation
  • Best when used exclusively with Cummins engines
  • Geared towards generators, not cars
Honorable Mention

Mobil 1 Turbo Diesel Truck Oil

Equipped to handle the wear and tear of a turbo-charged diesel truck, this entirely synthetic formula is ideal for warm environments. It provides reliable lubrication for enhanced engine life.
  • Built to work with modern diesel trucks
  • Suited to low-emission engines
  • Can pump at low temperatures for improved starting
  • Not rated for extremely cold environments
  • Only enough supply for a top-up and not for a complete oil change

Best Oils for 6.7 Cummins Reviews & Recommendations 2021

Finding an oil for your 6.7 Cummins is all about something able to withstand demanding conditions. The Quaker State 10W40 Protective Oil exceeds these demands, coming complete with powerful additives to address wear. It is geared towards rides with over 75,000 miles on the odometer. Higher-mileage Cummins engines tend to become oil-guzzlers, requiring top-ups more frequently than younger counterparts. It could be due to the added demand on the engine or as a result of leaks from cracked seals. To address this, the Quaker State oil is complete with conditioning additives that treat seals and put a halt to leaks. It keeps your selas working while also incorporating some extra additives to reduce adjustment friction and slow oil consumption. Powerful and reliable, this diesel oil can help extend your engine’s lifespan while also enhancing its function. 

One criticism about this oil is in the packaging. It comes with over a gallon of contents, yet the handle has no grip accommodations and the spout is too broad. Be sure to use a funnel when dealing with this oil to prevent spills.


Vehicle costs add up, from fuel to transmission fluid to oil. To shave a few dollars off this regular expense, the Cummins Onan 15W40 Oil is a worthy candidate. For starters, it has a universal compatibility rating, meaning you don’t have to worry about interactions with your existing oil. Despite being so reasonably priced, it doesn’t skimp in terms of quality. This oil is designed to work specifically with Cummins systems, meaning it is able to efficiently limit oil consumption. It is particularly useful at warm temperatures, where viscosity is prone to rapid increase. The friction regulators included as additives prevent this from compromising lubrication. By also addressing oxidation damage, this oil is able to help your engine perform more reliably. Ideal for anyone working on a budget, this is a worthy value pick. 

Bear in mind, though, that while the oil comes at a great price, it comes in a small quantity. For top-up use, it’s great. For an oil change, you’re going to need much more oil to get the job done.

If you live in an area more prone to snowstorms than heat waves, the Mobil 1 Turbo Diesel Truck Oil is a solid candidate. It stands out from the other candidates through its modern technology, including advanced additives to protect your vehicle well. It is meant specifically for vehicles handling the impressive horsepower supported by a 6.7 Cummins. By reducing the oil loss and improving fuel economy, it helps your whole ride function better. Meant to be compatible with any type of oil on the market, it is particularly useful with modern vehicles. If your ride is equipped with Exhaust Gas Recirculation, meant to limit emissions, this oil is particularly useful. Since these eco-friendly features impact the heat in the system, as well as oxidation effects, it is important to find an oil that can keep up with the demand. Mobil 1 is formulated to handle adversity, making it deserving of a shoutout on this list. 

Of course, nothing is perfect. This oil is a 5W40 after all, and the smaller the number to the left of that W, the more it is geared towards cold weather. Be sure to keep your climate in mind when making your pick. If contending with heat, look for something designed with the proper viscosity for hot situations.

Shell Rotella T6 is a state-of-the-art, fully synthetic motor oil blend that’s formulated to improve fuel economy up to 1.5 times its usual level. Its Triple Protection Plus technology might sound made up, but it’s actually a trustworthy mixture of additives that works to keep a Cummins engine safe from deposits.

What really got Shell Rotella T6 on our list is its performance in turbocharged engines. If you’re a turbocharger enthusiast who’s afraid that a 5W-40 oil will never hold the viscosity that you need to maintain pressure in a powerful engine, worry no more. This lube outperforms a lot of zero-weight manual-recommended oils.

Beware if you buy: Shell has a nasty habit of failing to fill the bottles all the way. It’s a great-quality oil, but you might have to buy 2 gallons just to ensure you have one. This can result in shipping issues, since the air gap leaves the plastic more vulnerable to impact. That said, it’s a good-quality oil, and the risk of damage is limited, keeping this synthetic oil on the honorable mention list.

Given the number of times Valvoline has showed up on this list, you shouldn’t be surprised to see the brand again. This time, we’re featuring its high-mileage solution, which is available in a wide range of sizes and viscosities.

In Cummins engines with more than 75,000 miles on the odometer, Valvoline high-mileage oil cleans out sludge and prevents new deposits from forming. It includes the extra detergents and protections older engines need to reverse wear. The seal treatment performs especially well—we’ve seen it stop leaks altogether and keep powerful engines running quietly at more than 200,000 miles. It also comes at a great price.

What’s the catch? This is a synthetic blend, not fully synthetic or Dexos-certified, so it might not be the right choice for aging GM vehicles. Don’t believe any seller who tells you it’s Dexos. Also, like many motor oils sold online, there’s a risk of the caps leaking.

This engine oil is similar to the Shell Rotella T6 we spotlighted above, with a few key differences. While Rotella T6 is completely synthetic, T5 is a synthetic blend that includes some crude products. That’s not a knock against it, though: It’s a low-ash, low-emission motor oil that’s perfectly suited for use in modern engines.

If we had to describe Rotella T5 in one word, it would be flexible. We don’t often see oils with the versatility to work in a Cummins 6.7, motorcycle, ATV, lawnmower, and chainsaw. It promises increased fuel economy and wear protection, and delivers on both counts. We especially like how well it maintains pressure in turbocharged engines.

One issue is that, while it’s a good oil, the cap leaves something to be desired. The threading can chip, making it almost impossible to get the seal back. Since it comes with a whole gallon, you’ll probably need to store it. Be careful when opening and retightening it, and you should be fine. 

The last entry in our list of favorite engine oils for a Cummins 6.7 is this synthetic blend from Chevron. Delo 400 XLE is formulated to clean out deposits, protect turbocharged engines, and maintain rigorous modern emissions standards. One gallon comes at an economical price, but that’s not all it offers.

Delo 400 XLE performs well as a mixed-fleet oil. Get a case of it, and you can boost the fuel efficiency of gas and diesel engines on cars, trucks, boats, and outdoor equipment. We saw the best results at searing highway temperatures, where other oils break down under the strain. Despite not being explicitly a high mileage oil, it also works well above 200,000 miles.

The only drawbacks of going with this oil is that it’s not a full synthetic, which might not grant the protection recommended by your owner's manual. The bottle is also poorly designed, with the handle on the same side as the spout, making it a bit hard for people with mobility issues to pour correctly.

Our Verdict

Why Trust Us

Our reviews are driven by a combination of hands-on testing, expert input, “wisdom of the crowd” assessments from actual buyers, and our own expertise. We always aim to offer genuine, accurate guides to help you find the best picks.

Learn more

The versatility and efficiency of our top pick, Quaker State 10W40 Protective Oil, is why you should try it. If you’re looking to save money and preserve quality, you can go with the Cummins Onan 15W40 Oil, a clear value pick. Whatever mileage you have and terrain you face, there’s an oil out there for your truck. 

Types of Oil for 6.7 Cummins

Synthetic Oil

One of the most modern 6.7 Cummins diesel systems, the turbo 2021 has an impressive compression ratio of 16:2:1 when in high output. This means the engine undergoes combustion at high heats and high pressures. Synthetic oil is a preference for handling these conditions, since it is able to withstand that extra strain on a molecular level. Yes, it comes at a higher cost because all the materials are artificial. However, you can get these oils at various viscosities and with different treatments, customizing the selection to your pick. The key takeaway: Synthetic oil is tops for vehicles under strain like pickup trucks.

High-Mileage Engine Oil

In the vast majority of cases, high-mileage engine oil is a subtype of synthetic diesel oil that is meant for vehicles with over 75,000 miles on the odometer. In theory, you can get upwards of 300,000 miles out of these engines, but once the mileage stacks up, switching oil is advisable. High-mileage oil is designed with the standard base oils, though includes additives like conditioning agents and oxidation preventatives. It softens seals, restoring them to proper function (provided the damage isn’t too extensive). The key takeaway: High-mileage engine oil is meant for older 6.7 Cummins engines. 

High-Viscosity Motor Oil

Viscosity matters. If the oil is too thin, then it won’t effectively complete its task. If the oil is too thick, it can’t move throughout the system. Since this factor directly impacts the oil’s ability to lubricate, finding the right viscosity is essential. High-viscosity oil lubricates more evenly, simply because it’s slippery and can coat the parts quicker. The SAE J300 viscosity chart details the specific metrics, so you can interpret coded viscosity notes like 15W40. The number to the left is how it handles cold. The number on the right is how it handles heat. Use the viscosity breakdowns, consider your environment, and pick accordingly. The key takeaway: When in doubt, choose high-viscosity oil.

Detergent Oil 

A popular type of oil, while all oil for 6.7 Cummins engines are made out of a set of base oils, the additives used to enhance performance vary. Though you can find some oils entirely free of detergents, these useful chemicals are effective at scrubbing out imperfections in the oil. Addressing deposits while also performing all the essential tasks of a motor oil, because of the chemical nature of magnesium sulfonates (the most common detergent), it retains structural integrity under pressure and heat. Plus, you don’t have to change the oil as frequently if you use a detergent option. The key takeaway: Detergent oils are a vast improvement on non-detergent motor oils. 

Conventional Oil 

Taking raw crude oil and refining it into a workable motor oil for your ride, conventional oil is the traditional approach to running your engine. It dates back to when Castrol first used mineral-based castor oil as an ingredient. Now, while you can find it on the market, it is definitely less common. This is largely due to the higher ratio of imperfections. It’s cheaper, but both in terms of quality and price. The imperfections may not result in issues right away, but using this type of oil can lead to issues. The key takeaway: Natural is great in theory, but synthetic oil takes the cake for 6.7 Cummins engines. 


  • $17 to $35. In this category, you can get up to five quarts of oil. It can be a full synthetic or synthetic blend. Some of the products come in one-gallon containers, others in five-quart or smaller containers. Viscosity ranges are 5W-20 to 15W-40.
  • $35 to $80. This category features a similar viscosity as the lower price range but you can get as many as three one-gallon containers for your money. Only full synthetic oils are found in this price range.
  • $80 and up. This range offers five-gallon pails of synthetic motor oil for your Cummins 6.7 engine. Viscosity ranges are from 5W-40 to 15W-40. This price category includes one oil that is specially blended for Ford under the Motorcraft name. 

Key Features

Lubricating Power

Obviously, you want the oil you choose to do its main job: lubricate the components of your Cummins 6.7 diesel engine. The OEM recommendations can guide you here, but you may want to read what others are saying about the oil you are considering with regards to its lubricating power. If the oil does not do this main job correctly, efficiently, and for a good price, it’s not the oil for your truck.

Weather Considerations

You want your oil to protect your engine in extremely cold and extremely hot weather. It can’t thicken too much in the winter or thin out in the summer, or it could inhibit proper starting and operation. Dust and dirt conditions are also a consideration. If you work in dusty, dirty areas, or drive off-road, your oil needs extra detergent power, and your engine will need more frequent oil changes as well. 

Environmental Impact

Many drivers are concerned with how their vehicle affects the environment, especially air pollution. Some diesel oil producers specially formulate some of their products to help reduce soot and nitrous oxide emissions. Others formulate their oil so it works best in the newer emissions-treatment engine designs. 


  • Always check your owner’s manual for the recommended oil for Cummins 6.7 engines. If you don’t go with the recommended oils, make sure the oil you choose meets or exceeds certain American Petroleum Institute (API) and National Institute for Automotive Service Excellence (ASE) standards.
  • Oils are carefully formulated to operate in specific temperature ranges. Buy the proper weight for your environment and season. A lower first number is a thinner base oil for extremely cold temperatures. 
  • Be careful when changing your oil to not over or under fill your Cummins engine. Too much oil in the crankcase/oil pan can create excess pressure, which can push oil past seals and cause damage. 
  • When changing your oil, it’s is a great time to change the air and fuel filters as well. Clean air and fuel filters will help your engine run more efficiently and cleanly, giving you better mileage. 


Q: What’s the difference between 5W40 and 15W40?

The number to the left of the W refers to the viscosity in cold situations. The number to the right references its thickness in hot settings. To achieve the properties of the 5W standing, the oil is synthetically made. Oil that is 15W40 may be synthetic or blended, though is more likely to include mineral grade components. If you’re dealing with cold-starting the Cummins, 5W40 is preferable. Dealing with a heatwave? Look for 15W40 for its high heat tolerance. 

Q: How much oil does my Cummins take?

It’s always best to follow the manufacturer recommendations. The specific amount of oil required will depend on the make and model. Many vehicles use a 6.7 Cummins, with most requiring 12 quarts for a complete oil change. For top-ups, it depends on your vehicle’s condition and the oil you’re using. Cummins are known for consuming a lot of oil, especially the older models. 

Q: How many miles does a 6.7 Cummins last?

Cummins was the first company to offer 100,000-mile warranties, so the brand stands behind its products. It’s reputed that you can get up to 350,000 miles out of the vehicle, but that requires pristine maintenance: regular oil and filter changes, responsible driving, and amenable road conditions. You can expect at least 100,000 miles, but after that threshold, it becomes more of a factor of wear and tear, climate, and driving habits. Take care of your Cummins and it will return the favor. 

Q: How often should you change oil in a 6.7 Cummins?

Follow the official maintenance schedule (especially if you’re on any kind of service contract). The frequency depends on your vehicle’s age, any existing damage, road conditions, and the type of oil. Because it also varies by the make and model of the vehicle, consult this chart to be sure. It’s best practice to change your oil every 15,000 miles; but, if your warranty says to do it sooner, stick to those parameters.

Q: What weight oil should be used in a 6.7 Cummins engine?

Cummins specifically recommends two Valvoline oils for its engines. The 15W-40 oil is for temperatures above 0 degrees Fahrenheit while the 5W-40 is for extremely cold temperatures. 

Q: Are synthetic oils better for 6.7 Cummins engines?

That’s open for debate. Some manufacturers and engine builders state that synthetics are better, while others prefer blends. What is universal is that the colder the environment, the lighter weight the oil needs to be to reduce wear during cold starts. 

Q: Is Valvoline Premium a good motor oil for 6.7 Cummins engines?

Valvoline Premium Blue and Premium Blue Extreme motor oils are specifically recommended by the Cummins factory. Cummins has tested these oils extensively and determined they have characteristics that make them ideal for diesel engines.