Best Oil For 6.7L Cummins – 2021 Buyer’s Guide

| Last Updated: December 24, 2021

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Oil is possibly the single most important component of your truck’s engine – so you should definitely make the right decisions when it comes to what kind of oil you want to put in your truck. We have compiled a list of some of the best engine oils we can find – read on to learn more.

Comparison of the Best Oil For 6.7L Cummins

  • Versatile – can be used in other vehicles
  • Will make your truck engine run more smoothly
  • Good oil to use in a location with varying temperatures
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  • Doesn’t have a strong odor when changing
  • Will decrease oil consumption for your engine
  • Widely distributed – you will always be able to find it
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  • Jugs have a wide mouth for easy pouring
  • Oil is specifically designed for working trucks
  • Versatile, can be used in other kinds of engines
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How Often Should You Change Your Oil?

There is no absolutely straightforward answer to this question, because it depends both on the model of your car and what you are actually doing with your car. A good rule of thumb is to change your oil every 5,000 miles. If you are putting your engine through its paces, though, either by accumulating a lot of miles in a short amount of time or by doing a lot of towing or otherwise enacting stress on your car, it can helpful to change your oil at closer to 3,000 miles. Oil changes are incredibly important for the functioning of your car, and if you do not change your oil when necessary, you will likely have to pay bigger bucks for more problems down the line.

Types of Oil Explained

Not all engine oil is the same, contrary to popular belief. Here are some common different types:


This is the most common type of engine oil. Conventional oil is refined from crude oil that is mined from the ground, which means it is not exactly the most environmentally friendly option. It is often, however, the cheapest option.


Synthetic oil is just that: synthetic! It is created in a factory or lab as opposed to being mined from the earth. It is often much more consistent than conventional oil since it is created under controlled conditions. It is also often much more expensive.

Synthetic Blend

If you want to strike a good balance between consistency/environmental impact and price, synthetic blend oil is the option for you. It is a mix between conventional oil and synthetic oil, so it has some of the benefits and drawbacks of both.

What Makes Quality Oil Stand Out?

As mentioned above, there are some oils that are more high quality than others. Here are some of the benefits you receive when you go with a quality brand:


This quality mostly applies to synthetic oil, as was discussed earlier in the article. It is definitely a bonus to know that no matter what, the oil you are buying will always perform in the exact same way. The value of reliable engine oil cannot be overstated.

Time Between Changes

Although it is always a good idea to at least check your oil every 5,000 miles, there are definitely some types of oil that will make it so that you do not actually need to physically change out your oil at that point. Quality oil can save you some money on the number of oil changes you have to undergo.

Ease of Access

One of the ways to identify a high quality, reliable oil brand is to make sure you have access to it wherever you go. The best oil brands will be sold widely, so you never have to worry about not being able to have access to your oil when your engine needs it, no matter where you may be located.

Review of the Best Oil for 6.7L Cummins

Now that you have a stronger background on engine oil, let’s check out some actual products:

1. Rotella T6 Synthetic Diesel Motor Oil 5W-40 CJ-4


  • Versatile
  • Synthetic
  • Can run for 6,000 to 8,000 miles before your truck will require a change
  • Will help your engine continue to run well even if it has upwards of 300,000 miles


  • Volume of oil containers does not match volume on truck oil canisters

The Rotella T6 Synthetic Diesel Motor Oil 5W-40 CJ-4 is some top notch engine oil! It will improve your entire engine’s running, making it much more smooth. It is excellent oil to use if you live in a location with widely varying temperatures, such as the high desert, and it makes cold starting your engine a lot easier.

Plus, it is versatile, as it can be used in a lot of different applications for vehicles beyond just your truck, including motorcycles. It is widely distributed, so you will always be able to find some Rotella oil whenever you need it, even if you are traveling in an unfamiliar location. And its synthetic nature makes it significantly more thick than conventional oil, which means it will take a longer time for your truck to burn through all of it and therefore will require fewer oil changes.

Bottom Line

The Rotella T6 Synthetic Diesel Motor Oil 5W-40 CJ-4 is a fantastic example of great engine oil. It can be inconvenient to add the oil to your engine, though, as the oil container is not the same size as your truck’s oil canister.

2. Valvoline 15W-40 Premium Blue Diesel Engine Oil


  • Widely distributed
  • Will decrease your truck’s oil consumption
  • Will make your engine temperature run more smoothly
  • Cummins recommends this oil specifically for use in their engines


  • Not synthetic

The Valvoline 15W-40 Premium Blue Diesel Engine Oil is fantastic engine oil that will be a benefit to your truck. It will decrease your truck’s oil consumption, which improves engine functionality in a number of ways. It is widely distributed, so you will always be able to find this oil whenever you need it, wherever you are.

It is not an unpleasant experience to change out your oil when you are using this Valvoline product, as it does not have a strong odor. And, you fortunately will not need to change out your oil that often when you are going with this oil as opposed to competitor brands – users report that they only need to change their oil around every 10,000 miles. Not a bad deal at all! There is not much to dislike with the Valvoline 15W-40 Premium Blue Diesel Engine Oil.

Bottom Line

The Valvoline 15W-40 Premium Blue Diesel Engine Oil is a great option for your engine that will allow you to go for longer between oil changes. However, it is not synthetic.

3. Super Tech Heavy Duty SAE 15W-40 Motor Oil


  • Specifically designed for working trucks
  • Super Tech provides good customer service
  • Jugs are sealed with foil and have a wide mouth for easy pouring


  • Has a high zinc concentration

The Super Tech Heavy Duty SAE 15W-40 Motor Oil is the oil for you if you are putting your diesel engine to work! This oil is specifically designed for use in working trucks that are hauling heavy loads or otherwise putting a lot of strain on their engines. Of course, this oil can also be used effectively in trucks that are simply going to be used for street driving. In fact, there are not many vehicles this oil could not be used in, as it is incredibly versatile.

It can be used in gasoline engines in addition to diesel engines, meaning you could easily use it in your generator or lawn mower. When it comes to diesel engines, it will work well in turbo charged AND low emissions diesel engines, so it really hits both ends of the spectrum. And to top it all off, it also works great with farm equipment.

Bottom Line

The Super Tech Heavy Duty SAE 15W-40 Motor Oil is probably the most versatile type of engine oil you will be able to find on the market today. It does have a high zinc concentration, which could be worth keeping an eye on.


Engine oil is incredibly important, for a wide variety of different aspects of your truck’s functioning. It is definitely not a product you want to compromise on. You will not be able to go wrong with any of the oil types we analyzed above – just choose what is best for you and your truck!            

Sean comes from the forums actually and drives an OBS Ford. He writes fantastic DIYs and knows his way around a camera, too. We keep him caffeinated and away from DPF filters to avoid another rant about recent emissions restrictions.