Motor Oil: Ultra-Thin Is In

Working towards impending requirements for greater fuel efficiency and lower emissions, OEMs are looking at everything that will help – and one of the key elements is creating more fuel efficiency in the engine through the use of thinner oils.
“Improving fuel economy and complying with stringent worldwide government regulations and standards to reduce greenhouse gas emissions are the main reasons behind the shift to lower-viscosity-grade engine oils, while maintaining durability,” explains Jaideep Sarnaik, an engineer at the Veedol technical office’s India facility. 
“Some of the ways of achieving better mileage can be by reducing vehicle weight, improving aerodynamics, conversion to hybrids and electric vehicles, etc. But the most proven method of both improving efficiency and reducing GHG emissions is through engine oil viscosity reduction by using appropriate base oils, viscosity modifiers, and other performance-enhancing additives,” adds Sarnaik.
“There are going to be some major changes to motor oils in both the passenger car and heavy-duty diesel arena,” explains Blaine Sherwood, a chemical technologist with Irving Blending & Packaging.
“The industry is now gearing up for the new CK 4, which will be licensable by 2016. With further emissions regulations being passed through the Environmental Protection Agency, heavy-duty engines are being designed to produce lower emissions. These changes will put higher stress on oil, and thus new formulations are necessary to ensure engine life longevity. Included in the changes are specialized additive technology to reduce engine wear, deposit control, tighter shear stability, and reduction of sulfated ash,” adds Sherwood.
In the passenger car arena, the industry is gearing up for the launch of GF6 in 2016. “Engines today are getting smaller, more efficient, and more powerful due to turbo and multi-valve designs. The oils need to be formulated to work within stringent tolerances that will be covered by the new GF6 guidelines. Some of the attributes of these new oil formulations will be greater fuel efficiency that is dependent on a more diverse weight of oil. Another major improvement will be that the new formulations will be able to handle higher heat tolerances produced by these smaller engines. As this technology is still being developed, it is difficult to determine exact changes, but on a high level you can expect greater fuel efficiency, rise in synthetic offerings, increased wear protection, and environmental stewardship,” explains Sherwood.
The current CAFE (Corporate Average Fuel Economy) standard for average required fuel economy is 34.9 mpg. In 2016, this requirement will go up to 37.8 mpg. By 2025, all vehicles and light-duty trucks sold in the United States will have to post 54.5 mpg of fuel efficiency, a near-doubling of today’s approved mileage standard. They will also have to produce significantly lower emissions as well.
To meet those standards, carmakers are pushing engine designs to improve fuel efficiency and reduce emissions. Honda is the leader of the OEM pack that is pushing the limits on oil viscosity and smaller, direct injection engines. These smaller-displacement engines are being placed in mid-sized vehicles. These are very high-tech engines that work much more powerfully than before.
Design advances like these are placing unique challenges on oil blenders, as these new thin ILSAC GF-6 motor oils have to meet stringent specifications. In fact, some enginemakers, like Honda, are now producing engines that can operate on oils that are going to be even thinner than the 0W-20/SAE 20 motor oils that will be coming out in 2016 under the ILSAC GF-6 specifications.
Honda has developed engines that operate on oils that will have a 0W-16 viscosity grade approved by the SAE. By going to a thinner oil, it is easier for the engine to run, less energy is required to pump the oil around the engine, and there is less resistance to movement of engine parts within the oil, which in turn improves fuel economy. But the oil film between moving parts like bearings, or where the cams meet the lifters, gets thinner, so you also tend to get more wear.
“The main difference is the reduction of high-temperature high-shear viscosity (HTHSV). SAE16 has the lowest value of HTHSV at 2.3 cP against 2.6 cP by SAE 20,” explains Sarnaik.
“Engine oil tends to shear in a running engine. HTHS occurs in various parts like bearings, piston rings and the valve train. Proper HTHS viscosity benefits in engine wear and fuel economy. Oil should form a protective film, but at the same time it should not be too thick, [which can] result in energy loss. HTHS plays an important role in fuel economy and durability of the engine,” adds Sarnaik.
SAE16 is already the new viscosity classification that has been added to the SAE J300 standard as a lighter-weight alternative to SAE 20 and other non-winter engine oil grades. Oils used in this grade will have a viscosity of either SAE 0W-16 or SAE 5W-16. SAE XW-16 viscosity-grade oils should provide significant fuel efficiency benefits in engines designed to run on low-viscosity engine oils.
Viscosity of engine oil can impact fuel economy. A lower viscosity grade can help reduce pumping losses and provide improved fuel economy; however, if the oil is too thin, excessive wear can result. The correct balance between viscosity and wear is therefore critical to maximizing fuel economy and providing excellent wear protection.
“The viscosity of oil is one of its most important characteristics. An engine has a massive amount of internal moving parts; each one of these relies on film thickness to prevent metal-on-metal contact. It is very important to follow the OEM recommendations on what type and grade of oil to use in a vehicle; the manufacturer has chosen these to optimize performance in that specific engine. If the oil is too light, the result will be increased wear within the engine. When the oil is too heavy, the oil will cause the engine to work harder, which will increase heat and decrease fuel economy. Your vehicle’s oil has been specifically chosen to optimize engine operation; going against the manufacturer’s suggestions does not only cause internal damage but could also void warranty,” explains Sherwood.
Key differences between GF-5 and GF-6 and GF-6B that jobbers need to know:
When GF-6 standards kick start in 2017, to avoid confusion amongst users, ILSAC GF-6 will actually be split into two potential specifications: GF-6A and GF-6B. The principal difference between the two categories of oils concerns viscosity grade and HTHS performance.
GF-6A will be backwards compatible, meaning that it can act as a straight replacement for GF-5 and can be used in all applications currently approved for GF-5. They will be represented by the Starburst/Certification Trademark, and would provide a new performance level of engine oil for spark-ignited internal combustion engines.
GF-6B will be completely unrelated to GF-5, and will be even lower viscosity, leading to a unique formulating approach where the base oil selection, the balance of additives, and the viscosity modifier will all be critical aspects. The proposed GF-6B oils would provide the same performance as GF-6A, but with the aim of lower HTHS to deliver potential fuel economy benefits. This offers the possibility of potential GF-6B oils operating at viscosity ranges of less than 0W-20 once these new viscosity grades are defined and accepted by SAE.
With even greater emphasis on fuel economy due to dramatic increases in CAFE targets (54.5 mpg by 2025), viscosity grades for modern engines will continue to go lower in the future. Vehicle owners should be advised to always read and follow the vehicle owner’s manual for the correct engine oil, to maximize fuel economy and performance while achieving long-lasting engine durability.