Diesel engine oil market shifts to lower viscosity


The viscosity of the oil is tested in a lubricants laboratory.

GettyImages via Citgo Petroleum

By Benjamin Briseño

In the US heavy-duty lubricant market, the search for fuel efficiency is influencing the transition from SAE 15w-40 diesel engine oils to those with lower viscosity grades, such as SAE 10w-30. This change is accelerating as engine manufacturers adopt and expand lubrication recommendations for low viscosity SAE grades, and more and more large trucking companies are using them. Most are in the process of upgrading to SAE 10w-30, but based on the equipment manufacturer’s recommendations for temperature conditions, other viscosity grades in SAE 5w-X and even 0w-X are being considered.

In the past, there have been similar changes in preferred engine oil viscosity grades. One example is the transition of heavy-duty diesel engine oils in the 1980s from SAE 30 and SAE 40 single-grade viscosity to SAE 15w-40 multigrade viscosity. This change was driven by energy efficiency as well as the convenience of dealing with one viscosity grade all year round, instead of having to switch between lighter and heavier grades for winter and summer use. Some innovative commercial trucking companies started using SAE 15w-40 motor oils ahead of the general market to gain operational advantages over those using monograde oils.

Current trend and benefit of lower fuel costs

Innovators and early adopters keep abreast of new technologies or approaches and are willing to apply them as appropriate. Cross the chasm by Geoffrey Moore, Harper Collins Publishers. For motor oils, the gap between the early adopters of a new product approach and the rest of the market can be influenced by how quickly engine manufacturers adopt or support a new approach. There may be companies operating fleets of trucks or construction equipment willing to risk equipment warranties to gain operational benefits, but those in the mainstream pragmatic stream usually await acceptance from the equipment manufacturer.

Today, major diesel engine manufacturers such as Caterpillar, Cummins, Paccar and Navistar include lower viscosity grades in their CITATION SEB19 l 1033 oil viscosity recommendations (SEBU6250 Caterpillar Machine Fluids Recommendations, 2019). The lower viscosity helps meet US EPA energy efficiency standards, NHTSA Phase II, which came into effect on December 27, 2016. An SAE 10W-30, for example, can deliver up to 3%. more fuel efficient than an SAE 15W- 40. With the lion’s share of trucking operating budgets being spent on fuel costs, a potential reduction of 3% is a significant economic gain.

Engines used in transport vehicles, whether they are powered by gasoline, diesel or natural gas, convert a source of energy into energy which is then available for movement. Engine manufacturers are constantly looking for ways to make the process of converting the fuel source to available power more efficient; study all areas where electricity escapes before the “tire meets the road”. One of the areas considered is the oil used for the lubrication of engines. Engine oil provides cooling, cleaning, wear protection, rust and corrosion protection, and lubricity of moving mechanical parts. The presence of the oil decreases the friction of the metal parts against each other, but the oil itself creates a bit of energy loss through the friction of the fluid as it flows through the engine. The higher the viscosity of the oil, the greater this loss of frictional energy from the fluid.

Other advantages of low viscosity motor oils

Beyond fuel efficiency, an advantage of properly formulated engine oils with better flow characteristics over those of SAE 15W-40 grade, is the ability of the oil to reach the lubrication points more quickly when starting the engine. motor. This is especially important when engine operation requires frequent starts or in colder climates. Depending on the ambient temperature levels and the SAE grade used, the use of block heaters can sometimes be avoided. Avoiding the use of a block header adds energy savings to the count.

Using a low viscosity engine oil will reduce the loss of frictional energy from the fluid, but the oil should have sufficient viscosity to provide the oil film thickness necessary for adequate lubrication and maintenance. durability of the machine. During operation, the oil film varies throughout the engine. This results in lubrication modes ranging from full film to limit lubrication CITATION Jea18 l 1033 (Rensselar, 2018). The use of low viscosity engine oils affects the lubrication modes. The lower the viscosity, the more the potential to be in a limit lubrication mode increases. It is important that engine oil formulations take this into account, providing surface protection through all modes of lubrication. To maintain engine durability, equipment manufacturers take this into account when developing lubricant viscosity recommendations for new engine designs.

Since lower grade engine oils will exhibit less resistance to flow in an engine, engine operators should expect to see lower oil pressure readings than they are accustomed to seeing. with an SAE 15w-40. Another consideration is the operating conditions which can introduce abrasive contaminants into the oil. Abrasive particles larger than the oil film could accelerate wear. The importance of proper filtration in these environments increases with the use of lower viscosities.

Viscosity is only one aspect of heavy-duty diesel engine oil. There is a complex blend of various performance additives, coupled with stocks of selected lubricants that make up engine oil. Approaches to this blend continue to change as manufacturers’ engine protection requirements evolve. Industry specifications, such as API CK-4, ensure that motor oils meet protective performance requirements through various test protocols. Engine manufacturers will specify the oil performance classification and oil viscosity required for your machine. API CK-4 motor oils are backward compatible with previous API performance categories, but API FA-4 motor oils may not. API FA-4 engine oils take the high temperature and high viscosity requirements one step further than API CK-4, increasing the potential for fuel economy. For this reason, before using any API FA-4 engine oil, you will need to check your engine manufacturer’s recommendations, especially if you are using an older engine. Your lubricant supplier can also help you find the right engine oil that meets OEM requirements.

Future prospects

The trend towards low viscosity motor oils continues. Engine builders have included SAE 10W-30 in lubricant recommendations since the introduction of API CJ-4 in 2006. It has not grown much, but use of SAE 10w-30 is expected to increase. ‘accelerate. SAE 15w-40 has been the dominant viscosity grade over the past decades. Its usage has peaked and is now expected to decline by 30% by 2029, with SAE 10w-30 reaching approximately 40% of the US CITATION Inf20 l 1033 market (Infineum USA LP, 2020). Engine manufacturers are pushing their designs to meet fuel economy and emissions requirements. The recent introduction of Volvo VDS-5 specification could push the use of SAE 5w-X oils and increase market comfort with lower viscosity API FA-4 oils CITATION Inf20 l 1033 (Infineum USA LP, 2020 ).

Benjamin Briseño is the Lubricants Technology Manager at CITGO Petroleum. With over 36 years of experience in the lubricants industry, Ben has held various positions in technical services, product line management, sourcing and sales management spanning national and international markets. Ben holds a Bachelor of Science in Mechanical Engineering and a Master of Science in Engineering Management from the University of Texas at Austin.


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