Tighter emissions regulations are being implemented worldwide with a particular emphasis on carbon dioxide and fuel economy directives. Previously the focus for such measures has fallen largely on passenger cars, but governments are now starting to include heavy-duty trucks. According to Bengt Otterholm, Volvo Group lubricants coordinator, these rulings will have a significant effect on heavy-duty engine oil formulations.
Japan issued the worlds first fuel efficiency standard for heavy-duty vehicles, with an effective date of 2015, Otterholm told Unitis Mineral Oil Technology Conference in April in Stuttgart. The average target is a 12 percent improvement between 2002 and 2015. A fuel efficiency test is a part of the approval process and consists of a mix of results from a simulation program and actual engine measurements.
As part of this program, trucks and buses with a gross vehicle weight of more than 2.5 tons will display a sticker based on their performance in the JC08 or JE05 test cycles. Stickers will show one of three performance levels: 10 percent above the 2015 standards, 5 percent above the standards; and compliant with the standards.
China in 2010 adopted fuel consumption and CO2 emissions limits that applied to new heavy-duty trucks. Measurements are taken on a level road, at constant speed and vehicle load, Otterholm explained. For example, a semitrailer combination with a gross combined weight of 43 tons is permitted to consume 42 liters of fuel per 100 kilometers. This is not a particularly tough standard, but improvements are expected in the future. In 2015 China plans to implement a new standard that includes chassis dynamometer testing and computer simulation.
This year the European Commission will present a strategy targeting fuel consumption and CO2 emissions from heavy-duty vehicles, Otterholm said. It will include a certification method to quantify fuel consumption and CO2 emissions and most likely will be based on a simulation tool with parameters being verified by actual measurements. The initiative includes three projects. The first assessed the amount and reduction potential of greenhouse gas emissions from heavy-duty vehicles. The second involves proposing a method to quantify emissions for vehicles and vehicle components. The third is an extension of the previous project in which legislation will be drafted. A declaration of fuel consumption will probably come sometime in 2016.
The United States published standards that are scheduled to take effect next year, and new targets are expected for 2017. The standards call for new trucks to be equipped with government-approved features such as aerodynamic kits, and original equipment manufacturers can receive credits for installing so-called innovative technologies. The government foresees a phase two regulation in 2020 that could be harmonized with Europe. Canada and Mexico are likely to follow these standards.
Heavy-duty engine oil formulations will be impacted significantly by increased use of biofuel, as well as fuel economy standards. In the European Union, for example, most diesel contains 6 or 7 percent fatty methyl ester (FAME), designated as B6 or B7. But an increase to B10 is under discussion, and local use of B30 and B100 is likely. Otterholm said, The impact on the lubricant due to fuel economy demands will be on the viscosity profile, including viscosity grade, high-temperature high-shear (HTHS) viscosity, base oil viscosity and shear stability. Friction modification also will be impacted, although it has only minor effects in heavy-duty diesel engines. To date, however, friction modification effects have been poorly investigated.
Otterholm compared the effect of viscosity grade on fuel economy in simulated European long-haul tests. The results show lower viscosity oils improve fuel economy by about 1 to 1.5 percent.
European OEMs have set new performance targets for 2014 and 2016. A major goal is biofuel compatibility, and an engine test is under development by CEC (the Coordinating European Council for the Development of Tests for Fuels, Lubricants and Other Fluid). Biofuel can accelerate oil degradation by increasing oxidation, depleting TBN and increasing sludge.
The primary rating criterion for the new test is piston deposits with sludge as a secondary parameter. Oxidation behavior of engine oils with the addition of biofuel also will be evaluated in a laboratory glassware test under development by CEC.
Although fuel economy is an important goal, Otterholm foresees no new test requirement. Fuel economy will be improved by eliminating the HTHS viscosity restriction. However, the specification will include the same or better wear performance requirements as current oils.
In North America, PC-11 is targeted for 2016 and is expected to provide improved oxidation stability, aeration, scuffing and adhesive wear and shear stability as well as biodiesel compatibility. PC-11 will include two fuel economy subcategories with corresponding performance levels. The first preserves historical heavy-duty oil criteria and provides backward compatibility. The second provides fuel economy benefits while maintaining durability and relaxing HTHS viscosity restrictions.
Finally, Japanese OEMs are developing new tests to replace obsolete hardware. The Hino N04C piston cleanliness test will replace the Nissan T025 engine, and the Hino N04C tappet wear test will replace the Mitsubishi 4034T4 engine. The specifications do not address fuel economy or biofuels because very little biofuel is used in Japan. The specifications also do not include HTHS viscosity restrictions.