The 10 Best Diesel Engine Oils
Special Honors
Dominator SAE 60 Dominator racing oil is 100-percent synthetic and specially formulated to meet the lubrication needs of the elevated rpm, extremely high temperatures, and shock-loading conditions generally found in competition scenarios. It is heavily fortified with both zinc and phosphorus for improved surface protection, and it features a proprietary friction modifier to minimize energy loss. amsoil.com
Editor's Notes
October 25, 2020:
Despite what marketing from major companies likes to try and make us believe, there isn't a lot of innovation in motor oils from year to year. Because of that, there weren't a lot of changes that needed to be made to the selections on this list. Now, we aren't saying that over time new formulas aren't created that help to better extend the service life of engine components, it is just that it doesn't happen quickly or very often. We also like to see a formula proven for a while, rather than just taking a company's word that their newest product is automatically the best, which is why we stuck with most of our previous recommendations during this update.
One notable change to our diesel oil rankings was replacing Total Quartz 9000 Energy with Total Quartz Ineo. The former was designed for engines without particulate filters, and since many jurisdictions are no longer allowing vehicles without them, we thought it better to include the Ineo series. While it is specially formulated for the needs of German engines, it does meet the technical requirements of diesel vehicles from General Motors, Hyundai, and Kia, too.
Though many oils are suitable for a variety of engines, it is generally best to use them in the kinds they are designed for. So, while Total Quartz Ineo could be used in heavy old trucks, it performs best in modern multi-valve engines quipped with turbochargers and direct injection technology. The same goes for Lucas Magnum CJ-4. While it could certainly serve well in enough in a light-duty passenger car in a pinch, it is best reserved for heavy-duty trucks. Similarly, though Chevron Delo 400 XSP won't harm a gasoline engine, you would be better off using something from our synthetic oils list that was specifically designed to handle the different environment found inside of a gasoline engine.
August 16, 2019:
Diesel engine oil comes in a variety of different formulas, and while they will all lubricant your engine components, some perform better under certain conditions than others. For example, Rotella T6 5W-40, Valvoline Premium Blue Extreme, and Mobil Delvac 1300 Super offer good thermal stability, allowing them to perform well in both hot and cold climates with as little change in viscosity as possible.
Castrol Edge C3 Advanced Full Synthetic, Motul 8100 X-cess, and Lucas Magnum CJ-4 will excel in hot conditions, such as those found in high-performance engines or tow vehicles that undergo a lot of strain. These formulas are designed with high thermal breakdown resistance and/or good oxidation stability.
When it comes to cold climates, Pennzoil Platinum Euro L and Total Quartz 9000 Energy are both good choices, as they retain decent pumpability in below-freezing conditions. This means cold starts will cause less damage over time, hopefully extending the service life of your engine.
Another thing to consider is synthetic versus mineral-based oils. While these terms may be slightly misleading, as the truth is they are both made from crude mineral oil, synthetics undergo a more advanced refining process that results in a cleaner, higher purity lubricant. This translates to a longer service life inside the engine and less buildup of sludge and other impurities. As you might expect though, this generally makes them more expensive. Items one through eight on our list are all full synthetics. The number nine product, Total Quartz 9000 Energy, is a mineral and synthetic blend, and the number ten item, Mobil Delvac 1300 Super, is made from all mineral base stocks, which is why it is the most budget-friendly option.
Now, just because you have bought a top-quality diesel oil that promises superior performance from of your engine doesn't mean that you should necessarily stop there. You may be able to see even more increased performance, better gas mileage, and lower engine wear by using an oil additive.
Additives In Diesel Engine Oil
Cars are expensive and most people will do just about anything to increase their car's lifespan.
Cars are expensive and most people will do just about anything to increase their car's lifespan. Hence, there is a large market for engine oil additives in the automotive industry. With all of the marketing hype on engine additive bottles, it is hard not to be convinced that you too should be using an additive in your oil, but is this really true?
Let's look at some of the facts. The American Petroleum Institute has specific grades for each type of engine oil. These grades are actually certifications that the oil contained within that bottle has everything needed to protect a certain type of engine. These certifications are listed on the bottle in shorthand with a format like CJ-4 or CI-4. Your vehicle's owner's manual will state what kind of engine you have, so you know what type of diesel engine oil you should be using.
All commercially available engine oils already contain a number of additives that turn standard base oil into a formula that is ideally suited for a specific engine type. Some common additives used in diesel engine oils include dispersants, friction modifiers, anti-acids, detergents, and viscosity modifiers. Each of these additives has a different function. Dispersants work in conjunction with detergents to take particulate impurities away from metal surfaces. Friction-modifiers help an oil deal with high pressure conditions, while viscosity-modifiers help an engine oil maintain the perfect viscosity across a wide range of conditions and temperatures. Anti-acids neutralize acids that are produced by engines as they run. This is just a small sample of the additives found in the average engine oil, the complete list of every additive type is significantly longer.
Since the commercially available formulas already include the best possible blend of oil and additives for your specific diesel engine type, there isn't much benefit of throwing extra additives into the mix, especially considering that the average consumer won't know what type of additive their engine oil will be lacking.
Gasoline Engine Oil Versus Diesel Engine Oil
There is a lot of confusion about the difference between gasoline engine oil and diesel engine oil. In essence, both diesel and gasoline engine oils are the same as they have a formulated blend of base oils with a variety of additives to change specific properties of the oil. The main difference between the two lies in which additives and the amount of each that are added.
Gasoline and diesel engines have different properties, which results in different contaminants in the crankcase, and the oil being exposed to different kinds of conditions. Gasoline engines wind up with a lot more moisture and tar in the oil, while diesel engines collect more carbon and become more acidic.
The main difference between the two lies in which additives and the amount of each that are added.
Typically diesel engine oils will contain higher levels of dispersants. This helps deal with the higher levels of carbon. They also have more anti-wear additives, usually in the form of zinc dialkyldithiophosphate (ZDDP), to help the catalytic converters handle the extra lead, phosphorus, and zinc they produce. Gasoline engines produce significantly less of these combustion byproducts and don't need as much ZDDP. Diesel engines also require a higher viscosity in their oil than a gasoline engine, which may produce too much heat from an overly viscous oil because their internal parts are moving at much higher speeds.
Overall, diesel engine oils will have more additive per volume than gasoline engine oils, mostly overbase detergents and dispersants, because, by their very nature, diesel engines subject their oils to harsher conditions and create a good deal more combustion byproducts.
With new, more expensive synthetic oils, it has actually become commonplace for companies to make dual rated oils, which can be used in both gasoline and diesel engines. These oils have an additive package that can work with both engine types, but it is best to choose an engine specific oil if possible. Otherwise you wind up with an oil that will work in your car, but isn't ideally suited to its specific engine conditions.
Common Diesel Engine Myths
A lot of misinformation about diesel engines is floating around out there, which has resulted in many people thinking diesel engines are less than suitable for the average home automobile, but this is simply untrue.
In addition to having more climbing power, they perform better at the higher altitudes.
One of the most common myths is that diesel engines are slow and sluggish. You might be surprised then to learn that turbo-powered diesels actually produce more torque at the lower RPM range. This makes them incredibly responsive and able to accelerate quicker than many of their gas counterparts. It also makes them ideal for climbing steep grades. In addition to having more climbing power, they perform better at the higher altitudes. This is because gas-powered engines operate at extremely specific fuel-to-air ratios and at high altitudes, air is thinner and the air-to-fuel ratio is off. Diesel engines don't require such a specific fuel-to-air ratio.
Another common myth is that diesel engines are dirty and belch out clouds of black smoke. While this may have been true in days past, now diesel engines have to meet the same strict EPA emissions requirements as gasoline engines. They accomplish this by adding a diesel particulate filter, which traps smoke from a diesel's engine. Once the engine's computer system determines that it is time to clean the filter, this extra soot is burned off automatically by the addition of a small amount of extra fuel in the combustion chamber.