The Most Popular Diesel Oil Brands Ranked Worst To Best

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Engine oil serves a number of purposes in one's vehicle. It forms a layer of protection on the metal parts of the engine as it warms up while mitigating and distributing heat. When the vehicle is running, the oil cleans the engine from water, dirt, and metal particulates.

Diesel oil, however, has a generally tougher environment to operate in as it must deal with factors like compression and soot accumulation. It needs its own set of additives to deal with those issues and is generally used in a higher viscosity than gasoline engines. For this diesel oil ranking, we'll be comparing gallon-size bottles of 15w-40, as that's been the standard for a while.

It's important to verify the right weight for a vehicle, and that information is in the owner's manual and usually on the oil fill cap as well. The owner's manual will also be the place to look for oil change frequency –- often the oil should be changed every 5,000 to 15,000 miles, but it's best to make sure. Finally, while one's diesel Ram 3500, F-350, or Yukon may suggest Mopar, Motorcraft, or AC Delco oil, there's a whole world of aftermarket diesel oils out there to try, many of which boast specs far beyond industry standard CK-4. Here, we're going to rank the best of them.

10. Hot Shot's Secret

Hot Shot's Secret is a newer brand compared to the centuries-old companies that will appear later on this list. However, Lubrication Specialties, Inc., the maker of Hot Shot's Secret, took a different approach to their business. Founded in a two-car garage in Ohio in 1997, the company focuses on solving specific problems that weren't being addressed in the lubrication industry.

"Powered by Science" — while a catchy slogan — means a lot more when the founder of the company is both a Certified Lubrication Specialist and an Oil Management Analyst. After being approached in 2005 to solve an injector issue with Ford's Power Stroke 6.0-liter engine, Hot Shot's Secret Stiction Eliminator was born. Since then, the company has grown by leaps and bounds, offering additives, motor oils, transmission fluids, and even fuel and oil analysis kits.

All of Hot Shot's Secret's engine oils are designed for diesel engines. The company claims the oil's additives improve fuel economy, reduce engine wear, and keep oil clean while increasing horsepower. While its most popular product on Amazon only has 66 ratings, it's still been selected as Amazon's Choice with a 4.7-star average. Hot Shot's Choice Green Diamond Synthetic also gets rave reviews from many sites and parts shops, earning them an entry-level spot on our rankings.

9. Lucas

Lucas is probably the best-known additive company in America, with a motor speedway and an NFL stadium in Indianapolis bearing the company's name. The company was founded by Forrest and Charlotte Lucas in 1989, and today it's run by his son and daughter-in-law, making it one of the most successful family businesses in an oil industry dominated by multinational organizations. Founded on the premise of providing solutions for industries not getting their needs served by larger oil companies, Lucas has become a mainstay in motorsports and outdoor applications as well as industrial and everyday driving uses.

Lucas is primarily known for its Stop Leak additives, but its vast array of lubricants and additives includes a couple of options for the diesel driver. One version of its Magnum 15w-40 is designed for pre-2007 diesel engines, and it's formulated to hold more soot in suspension than most 15w-40 oils, which should allow for extended drain intervals while prolonging engine life and preventing dry starts. 

More modern diesel engines can opt for Lucas' Magnum CK-4 diesel oil, which meets current industry standards and promises less soot and wear. This product only has 51 ratings on Amazon but boasts a 4.6-star average and has been labeled Amazon's Choice, which typically applies to products that are readily available, well-reviewed, and reasonably priced.

8. Schaeffer's

Schaeffer's started out as Schaeffer Manufacturing Company and was founded in St. Louis, Missouri. The company remains based there to this day, although it has evolved from a purveyor of soaps and candles into a worldwide provider of lubricants and additives. Food-grade lubricants, metalworking, industrial oils, and a number of other industries are served by the products from this family-owned company that got its humble start where the St. Louis arch now stands.

Schaeffer's is an interesting pick for our diesel oil rankings, especially since the company hasn't appeared on any of SlashGear's related rankings of oil brands. Schaeffer's has been in business for nearly two centuries, and its SynShield Durability Advantage 15w-40 diesel oil is very popular among diesel enthusiasts and truckers despite the slightly higher price tag. Promising great thermal stability, soot-busting performance, and even fuel savings, the lone 15w-40 offering from Schaeffer's is a high-quality, heavy-duty diesel oil that exceeds the industry standard API CK-4.

A common complaint used to be that Schaeffer's was a fantastic product that was difficult to obtain at a reasonable price. Schaeffer's own online Oil Shop makes its products available for delivery, although most products are only available by the case. However, with an Amazon storefront that carries many of its products in various sizes, Shaeffer's is now more readily available to its customers than ever before.

7. Liqui Moly

While Liqui Moly was founded in 1957, it wasn't until the late 1970s that the company entered the motor oil business. It cleverly added its molybdenum disulfide additive, the foundation of its operations, to these new motor oils. Beyond that, advertising that featured a pair of Volkswagen Beetles driving around Europe's Lake Constance with no motor oil — running instead using just MoS2 Oil Additive – demonstrated the impressive abilities of the brand's additives.

Germany's Liqui Moly makes three blends of 15w-40 diesel oil, with its Top Tec Truck being the most popular. The company says this oil provides the best wear protection and engine cleanliness, as well as the lowest oil consumption and highest engine efficiency, even with extended oil change intervals. To back that up, a limited warranty is provided to customers covering parts damaged if the oil is determined to be at fault.

There's very little review interaction on Amazon -– Liqui Moly's mineral-based high mileage Touring High Tech oil has the most, at 64 reviews and 4.5 stars – but the company has a great overall reputation, and the company didn't earn dozens of German motor oil awards by producing an inferior product.

6. Castrol

Castrol is the oil of choice for many auto manufacturers, including Honda, Jaguar, and Ford. Castrol was founded in 1899 and made an impact by providing oil to several land speed record-setters. It also made a point of advertising itself heavily when one of those sponsored vehicles won, rapidly growing the company's popularity at a time when that kind of fame was hard to come by.

Given the fact that Castrol is one of the best-known motor oil brands on the planet, one would think the company's diesel offering would be a favorite among motorists. However, there simply isn't a lot of chatter among gearheads when it comes to Castrol's offerings. Actually, one of the first search results is a forum last updated six years ago lamenting a lack of love for Castrol's 15w40 diesel oil.

In 15w-40 varieties, Castrol Vecton suggests a 45% extra performance reserve over industry standards, and yet an Amazon listing for the product only yields four reviews. CRB Multi is marketed as being versatile, with better shear stability and protection while conforming to API CK-4, but that product is also hard to find outside of NAPA stores. Meanwhile, Castrol's best-reviewed option on Amazon, the conventional GTX diesel oil – which still only has 75 ratings and a 4.6-star average -– is also out of stock as of this writing.

5. Red Line

Red Line began making lubricants for racing applications in 1979 and now produces more than 100 additives and lubricants for a number of applications. Red Line's devotion to synthetic oil comes from their use of ester and PAO bases, which are more expensive but provide better heat resistance.

Red Line's synthetic 15w-40 diesel oil is rated well on Amazon, averaging 4.7 stars but only 50 ratings. It's API CK-4 compatible, keeping up with the latest standards, and the company says the oil is popular with Chevy Duramax, Dodge Cummins, and Ford Power Stroke owners. However, Red Line is one of the more polarizing entries on this list.

While it's rare to see anyone actively deny the quality of its products, Red Line's high price is often cited as a reason to pass on it. At $61 a gallon, however, it is difficult to push this product over other, better-reviewed options that only cost half that much.

4. Mobil Delvac

Mobil is the largest oil company in the world and has had over 140 years of history to experiment and innovate. Mobil 1 topped SlashGear's list of the best synthetic motor oils, and the number of times customers brought in that product for oil changes during our experts' 15 years in the field is rivaled only by the number of folks who brought a case of the top-ranked oil on this list.

Mobil's entry on our ranking is Delvac, its series of diesel engine oils. 1300 Super is widely regarded as Mobil Delvac's best option, as it strikes a balance between engine life-extending benefits and cost. It has over 400 reviews on Amazon, and a 4.7-star average, which is very respectable.

Mobil Delvac Extreme, the next step up, features 46% more antioxidant and 44% more anti-wear additives than 1300 Super and is recommended for heavy-duty applications and heavy loads. It's not available on Amazon but can be found on NAPA and Advance Auto Parts' sites, where it sports 5-star reviews.

3. Royal Purple

Royal Purple is one of those brands that commands loyalty among its true believers. To be clear, it has earned that reputation by providing years of protection and performance to customers around the world. However, that purple dye just seems to do it for some people. Plenty of YouTubers and online forums run their own tests and surveys about the purple product, and the results are generally favorable.

Royal Purple's line of diesel motor oils is Duralec, and it's available in both Super and Ultra flavors. Additives promoting less engine wear, greater protection on startup, and better film strength to lessen metal-to-metal contact are just a few of the selling points on the slightly pricier Ultra formulation, but both are well-reviewed and trusted by diesel parts shoppers and Amazon customers alike, with an Amazon average of 4.8 stars among over 200 reviews.

While the price can be a little daunting, it should be noted that Amazon also offers bundles with Royal Purple brand filters to try to ease the strain on customers' wallets –- and those Royal Purple filters ranked highly on our list of the best oil filter brands.

2. Valvoline

Valvoline topped SlashGear's rankings of popular transmission fluids with a combination of a low price, high customer reviews on a number of sites, and a quality product. Those same factors nearly got the legendary motor oil maker to the top of our diesel oil rankings as well, if not for the juggernaut to follow. That doesn't diminish the fact that Valvoline puts out a great product, and one that has been trusted for generations.

Valvoline was founded in 1866, and since then the company has claimed such innovations as the first racing motor oil, the first synthetic blend, and the first high mileage motor oil. That innovation has led to Valvoline's Premium Blue diesel oils, which are designed to outperform industry standards in deposit and wear resistance and oxidation while also contributing to faster cold starts and better performance in hot weather as well. For those reasons, Valvoline's Premium Blue is the only engine oil endorsed and recommended by Cummins for both on-road and off-highway applications.

Over three thousand reviews of Valvoline Premium Blue on Amazon speak to its popularity, and its 4.7-star average reflects the positive experiences most customers have with the product.

1. Shell Rotella

Shell Rotella is the most popular diesel oil and it's not even close. It's the best-selling diesel oil on Amazon and boasts a great average rating and thousands of positive reviews. Still, does that make it the best? According to many customers, yes. The divide is very similar to that among synthetic oil brands, where Mobil 1 stands far from the rest of the pack as the clear winner.

Shell Rotella T6, in particular, is trusted and recommended by diesel truck operators around the world. Shell's Triple Protection Plus formulation promises protection against engine wear, deposits, oil breakdown (or shearing), and improved low-temperature flow. It's recommended for all kinds of diesel engines, from the white Ram 3500 your neighbor drives to semi-rigs. Amazon reflects these reviews from users of all walks of life, with a whopping 11,000-plus reviews and a 4.8-star average for a gallon of 15w-40 T6 full synthetic. The reasonable price for such a great product doesn't hurt either.

Unfortunately, 2022 saw many complaining about a lack of Shell's popular Rotella T6 oil on store shelves. However, with supply chain issues improving since then, all varieties of Rotella seem readily available for the thousands of drivers who trust their vehicles with the popular diesel oil.