As new technologies are developed and adopted within the automotive industries, they become the norm. It is often easy to forget the reasons why they were needed in the first place. This is very much the case with the evolution of lubricants from the relatively simple oils of 50 years ago, to the complex, high performance formulations that are in use today.
The role of the lubricant has been an essential component in the development of modern engines. As power densities and operating temperatures have increased, and exhaust aftertreatment devices have been added to enable engines to run cleaner and leaner than ever before, additional demands have been placed on the lubricants.
Particularly in the case of post-combustion devices or aftertreatment devices, such as EGR. A system designed to reduce automotive emission of nitrogen oxides (NOx). EGRs route exhaust gases into the intake manifold where they dilute the air/fuel mixture and reduce peak combustion temperatures, thereby reducing the tendency for NOx to form. (Exhaust Gas Recirculation. A system designed to reduce automotive emission of nitrogen oxides (NOx). EGRs route exhaust gases into the intake manifold where they dilute the air/fuel mixture and reduce peak combustion temperatures, thereby reducing the tendency for NOx to form.), diesel particulate filters (DPF) and selective catalytic reduction (SCR), the role of the lubricant has been a fundamental consideration in their application and effectiveness.
Equally important has been the role of 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. or the ‘Association des Constructeurs Européens d’Automobiles’, which is the automobile manufacturers association that represents Europe’s 15 most important car, van truck and bus manufacturers.
ACEAs oil sequences provide a core specification for oil manufacturers to ensure their products are compatible with the latest developments in European engine technology and that the lubricants satisfy key performance criteria.
Since the first ACEA oil sequence was issued in 1996, which replaced the former CCMC specifications, there have been nine updates, with a tenth scheduled for introduction during 2016.
So, with the latest 2016 ACEA sequences imminent, what is the relationship between aftertreatment devices, ACEA sequences and lubricant formulation?
ACEA Addresses 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.
The link between engine technology, oil formulation and aftertreatment has become ever more intertwined, and is driven primarily by increasingly stringent environmental legislations governing vehicle emissions.
Even though the first ACEA oil sequences were not introduced until 1996, the effects of emissions regulations began to be felt by the mid-1970s on the back of the first oil crisis, which hit the US and Europe, resulting in shortages of fuel and lubricants.
Action to address health and environmental concerns over vehicle emissions and pollution was initiated by the US Environmental Protection Agency (EPA), calling for the use of unleaded fuel only. Other countries followed suit, and Japan introduced its own emissions legislation as far back as 1976.The growing need for vehicle OEMs to reduce exhaust emissions, while improving fuel economy and engine efficiency, saw manufacturers embark on a process of engine development that ensured they hit the targets or face punitive financial penalties.
In 1994, the car had a power density of 39.6kW/litre, CO2 emissions were 189g/km and the oil drain interval was 15,000km using a 10W-40 lubricant. By 2014, however, the cumulative and sustained effects of stricter global environmental legislation and growing lubricant demands have had a considerable effect on the same vehicle parameters.
Power output density had more than doubled to 79kW/litre, CO2 had reduced by almost 35% to 124g/km and although the oil drain interval had remained unchanged, the lubricant grade was now a 5W-30. This same vehicle model is still in production and the next generation is planned to be capable of 35km/litre (100mpg), and have CO2 levels as low as 74g/km.
Emissions, Efficiency and Lubricant Design
Reduced emissions, however, are not just a function of engine efficiency. Post-combustion exhaust treatment systems, including catalytic converters, diesel particulate filters (DPF) and exhaust gas recirculation (EGR) systems are all now commonplace, and are constantly monitored while driving to adjust the fuel/air mixture and ignition timing to manage CO2; NOx and particulate emissions, as well as other contaminants.
Inevitably, exhaust treatment systems have also had an impact on the chemistry of engine oil. Combustion by-products, resulting from the burning of oil, such as A product of the combustion of metals commonly found in detergents. As a lubricant property, sulfated ash content is a measure of metal content (usually Zinc, Calcium, and Magnesium) and allows formulators to stay within specified limits in order to minimize the negative effects of abrasive ash particles. Sulfated ash is determined by charring the oil, treating the residue with sulfuric acid, and evaporating to dryness, the result being expressed as % by mass., phosphorous and sulphur, have been vastly reduced from oil formulations as they can block DPF systems. Modern low SAPS oils work in harmony with exhaust filtration systems to improve efficiency and extend working life.
Alongside this, higher power outputs, increased stresses within the engine and elevated operating temperatures, caused by more efficient combustion and the use of turbo systems, have created an increasingly hostile and challenging environment for lubricants.
To overcome this, lubricants have evolved from The primary or underlying fluid, usually a refined petroleum fraction or a selected synthetic material, into which additives are blended to produce finished lubricants. with simple additive chemistry to complex formulations that have applicability in a broad range of climatic, operation and equipment parameters.
A direct consequence of this evolution, which has been increasing in pace over the past two decades, is that older formulations cannot be used in today’s vehicles, as their design parameters are simply incompatible. Many modern lubricants are backwards compatible to vehicles using more conventional and traditional technology.
Throughout this ongoing process of change, ACEA has been at the centre of lubricant formulation by interpreting the needs of its members, and translating them into the key specifications on which many European formulations are based. Essentially, this provides the DNA map for lubricants that are compatible for current engine and aftertreatment technologies, as well as those that are being developed.
ACEA 2016 Adapts for the Future of Emissions
Because of this ever-changing regulatory framework, ACEA adopted a two-tier alpha-numeric system for its Oil Sequences, which not only provide a clear point of reference, but also a high degree of flexibility, allowing new ‘Sequences’ and specifications to be added when necessary. To learn more about the ACEA framework, read The ABCs of ACEA.
In terms of vehicle emissions performance, in 2004 ACEA introduced ‘C’ class oil sequences, which were designed specifically for the growing number of cars fitted with aftertreatment devices such as DPFs (diesel particulate filters) and TWCs (three way catalysts). These oils are also described as reduced SAPS oils, being specially formulated using lower levels of Sulphated Metallic deposits formed in the combustion chamber and other engine parts during high-temperature operation., Phosphorus and Sulphur to help avoid blocking of exhaust gas filter systems.
Jump forward to 2016, and the new ACEA ‘C5’ sequence is incorporated in the latest oil sequence revision, which also sees the original A1 and B1 sequences being dropped.
Clearly, the drive for fuel economy, lower emissions and greater vehicle efficiencies is still as strong today, perhaps even stronger, than it was when the original ACEA sequences were introduced so long ago.
Lubrizol’s commitment to the development of lubricant technologies through its advanced chemistry, intensive testing processes and commercial knowledge will help ensure these goals are met.