In Europe it is legislation that sets the mandatory emission reduction targets for new cars. The fleet average of 130 gCO2


/


km has been gradually phased in since 2012, but from 2015 100% of each manufacturer’s new car registrations must comply. The next target of 95 g/km will phase in from 2020 to 2021 and represents a 40% reduction compared with the 2007 fleet average of 158.7g/km.


some vehicles with higher emissions, provided they are balanced by sufficient vehicles with emissions below the limit. However, if fleet average CO2


Because only fleet average CO2 is regulated, OEMs can produce


km to €15 for the second, €25 for the third, and €95 for each subsequent g/km.


becomes payable by the OEM for each car registered. This ramps up quickly for each excess gram of CO2


emissions exceed the limit, a premium - €5 for the first g/


Many OEMs need to cut their CO2 emissions by more than 10 g/


km to meet the 2015 limits or face these penalties for non- compliance, which could run to billions of euros per annum for some. In their efforts to avoid these fines OEMs are looking for energy savings from every quarter – from the powertrain and vehicle itself and from advanced materials and fluid technology.


Low viscosity delivers fuel economy Reducing lubricant viscosity, which in turn reduces engine friction, is an effective way to improve fuel economy performance.


In the early days of fuel economy research, work carried out by Infineum on heavy-duty engines revealed that lowering a lubricant’s high temperature high shear (HTHS) viscosity could result in up to a 1.5% improvement in fuel consumption over the European Stationary Cycle (ESC) test. This might seem like a fairly small reduction but lubricant derived fuel economy comes at a smaller cost to OEMs compared with hardware improvement. And, when you consider the potential fines for non-conformance to EU legislation, OEMs see even these relatively small savings as significant contributors to meeting efficiency targets.


Over the years our research has given us a good understanding of the relationship between friction reduction, derived from using low HTHS viscosity lubricants, and fuel consumption over a variety of drive cycles and ambient conditions. As a result we have developed a formula for converting reduction in motored friction to percentage improvement of fuel consumption over the test cycle.


Trends in low viscosity fluids With tangible fuel economy gains to be made from lowering lubricant viscosity we can be fairly certain that there will be


a move to ultra low viscosity lubricants, particularly as CO2 legislation comes into force or tightens across the globe.


However, because vehicle population age and OEM market share both impact viscosity grade trends it can take many years for new viscosity grades to make up a significant portion of the overall market. If we look at the trends in North America as an example (Figure 1), SAE 5W-30 is currently the most common viscosity grade. But, it took from the late 1980s until 2006 for this grade to rise to the top market share position, and it will take a long time for it to exit the market - despite the fact that SAE 5W-20 and 0W-20 are now the most widely recommended grades for new cars.


It is likely that the new SAE 0W-16 grade will only be used in new vehicles, which means that we may not see significant volumes in the market until 2020, and even then it is likely to only account for a small percentage of total oil sold.


Despite their slow market penetration, ultra low viscosity fluids are on the increase and this North American picture is likely to reflect global trends.


Impact of specifications


Although the upcoming ILSAC GF-6 specification will introduce the new SAE 0W-16 grade, many OEMs suggest SAE 0W- 20 and 5W-20 will continue to meet their needs. Toyota has initiated a testing matrix to establish limits for SAE 0W-16 oils in the Sequence VID, which could potentially enable resource conserving to be added to these oils. However, industry has voted to amend ILSAC GF-5 so that the ‘Starburst’ cannot be used with SAE XW-16 grades before the ILSAC GF-6 first allowable use date.


SAE Technical Committee 1 has also approved a ballot to allow SAE 0W-8 and 0W-12 viscosity grades to be defined. Industry however has a long way to go to define the necessary specifications that will be needed to qualify such low viscosity oils.


Low viscosity and durability challenges Clearly the move to lower viscosities is coming, and we can expect this trend to be accompanied by a whole new set of challenges. The first is how to balance the desire for fuel economy with the need to meet the most challenging OEM and industry specifications to protect the engine and all its components.


Lower viscosity results in reduced oil film thickness and a decrease in the oil’s ability to keep the loaded contact surfaces in the engine sufficiently apart from each other. This can lead to accelerated wear rates, and even locally increased friction at some contacts, and it really makes little commercial sense to trade engine durability for fuel economy gains.


The results of one project carried out by Infineum indicated that, although specific engine components have higher wear rates as HTHS viscosity is reduced, it is possible to reduce lubricant viscosity to below 2.3 HTHS without significant risk. The study also demonstrated that, when using an oil with HTHS as low as 1.8, the only increase in wear rate was observed in the top piston ring – while those in the conrod bush, camshaft and cylinder liner remained low.


However, extensive engine testing with low viscosity lubricants has convinced us that the development of low viscosity lubricants must be approached with extraordinary care to ensure uncompromised engine protection.


Continued on page 8


LUBE MAGAZINE NO.125 FEBRUARY 2015


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