Squeezing Greater Efficiency Out of Heavy Duty Engine Oils
Courtesy of Engine Technology International
Increased fuel economy and reduced greenhouse gases are being supported by lower ‘high-temperature high-shear’ engine oil viscosity
The continuing environmental drivers and legislation for reduced Mobile sources - Pollutant exhaust gases created by the combustion of fuel. Water and CO2 are not included in this category, but CO, NOx, and hydrocarbons are and are thus subject to legislative control. All three are emitted by gasoline engines, while diesel engines also emit particulates that are regulated. Stationary sources - The release of sulfur oxides and particulates from power stations that can be influenced by fuel composition. Local authorities control the sulfur content of heavy fuel oils used in such applications. and increased fuel economy continues to force changes in engine hardware design around the world. Significant changes in heavy-duty diesel engine technology and operating conditions have resulted in engine downsizing, down-speeding, higher oil temperatures, stop/start technology, and variable valve timing, to name a few. At the same time, advances in heavy-duty diesel engine oils have played a vital role in enabling these performance improvements.
Using lower A measure of a fluid's resistance to flow. A fluid with a higher viscosity flows less easily. grades – moving from traditional 15W-40 to 10W and 5W viscosity grades – is now well accepted as delivering increased fuel economy and reduced greenhouse gases (GHG). At the same time, demonstration that hardware protection is not sacrificed is proven by stringent testing alongside millions of miles of real-world driving.
The viscosity of an oil is measured by The measurement of a fluid's resistance to flow under the force of gravity at a specific temperature, usually 40°C or 100°C. (KV) – the time that is measured for a fixed volume of liquid to flow through a tube under the force of gravity. However, in an operating engine, oil is exposed to more than just gravity, notably nowadays where it has to run in hotter and more severe operating conditions.
High-temperature high-shear (High Temperature High Shear. A measure of a fluid’s resistance to flow under conditions resembling highly-loaded journal bearings in fired internal combustion engines, typically 1 million s–1 at 150°C.) is the current industry standard test that best predicts fluid behavior in these more representative operating conditions. Within an engine, HTHS is relevant across the bearings, camshaft, and piston and liner areas. As with KV, HTHS is not new – with limits being explicitly defined within SAE J300 as far back as the early 1990s.
HTHS is designed to ensure that oils do not shear down at high temperatures and shear rates, which ensures that film strength remains acceptable for component longevity with thinner oils, and delivers even further fuel economy and reduced GHG.
Lower HTHS is actively being pursued by an increasing number of heavy-duty OEMs (including FPT Industrial and Scania), to move significantly below the long-established 3.5cP HTHS limit in conjunction with modern engine hardware designs.
Industry specifications are also being rolled out to reflect the needs from engine manufacturers. The API. The primary oil and natural gas trade association in the United States. API operates a voluntary licensing and certification program that allows engine oil marketers to use the API Engine Oil Quality Marks if their products meet specific requirements. (American Petroleum Institute. The primary oil and natural gas trade association in the United States. API operates a voluntary licensing and certification program that allows engine oil marketers to use the API Engine Oil Quality Marks if their products meet specific requirements.) will see the introduction of its first-ever split category of API CK-4 and API FA-4 in December 2016. While API CK-4 will offer backward compatibility (minimum 3.5cP), API FA-4 will offer fuel economy benefits through lower HTHS between 3.2 and 2.9cP. The European Automobile Manufacturers’ Association (European Automobile Manufacturers Association (Association des Constructeurs Européens d'Automobiles). The primary automotive standards organization in the European Union, ACEA defines performance specifications for automotive lubricants.) is likely to follow with a new sequence at 2.9cP HTHS in the next upgrade after ACEA 2016.
The focus on lower HTHS is gaining momentum as it is regarded as the latest view that more accurately mimics the engine oil behavior in the increasingly severe operating conditions. “Such a move to lower HTHS engine oils is complex,” says Keith Corkwell, global business manager for Lubrizol’s heavy-duty diesel engine additives segment. “The vital roles of the additive package, performance polymer and the The primary or underlying fluid, usually a refined petroleum fraction or a selected synthetic material, into which additives are blended to produce finished lubricants. need to work in harmony with the changes in engine hardware. Lubrizol backs this up with its extensive research, development and millions of miles of field testing in order to demonstrate proof of performance in real-world driving conditions.”
Lubrizol’s proven range of performance additives and polymer technologies can be tailored to meet the individual OEM’s specifications, designs and materials. All of these lower HTHS requirements can be met when the engine oil is included as an integral part of the design process, with all partners working in a close and cooperative environment to meet the same goal.