Continued from page 8 Downsizing 2.0


The sole orientation towards ever smaller but more highly charged engines (downsizing) is also currently being questioned. The ongoing downsizing of engines achieves optimum results, particularly when the engine is running at lower load. With the so-called ‘Miller-Cycle’ principle, a somewhat larger engine runs more efficiently with optimised intake valve timing, a broader speed range and a somewhat lower charge in the medium load range. At the end of the day, this allows more fuel to be saved than through maximum downsizing.


Another problem also affects engine oil quality requirements: so-called ‘Low Speed Pre-Ignition (LSPI)’ – also known as stochastic pre-ignition. Here, premature self-ignition of the main fuel charge occurs in turbocharged petrol engines – something which should of course be avoided. For this reason, magnesium or molybdenum are often used as additives for the engine oil rather than the calcium previously used. It is not known what actually causes the pre-ignition, but what is certain is that besides the engine design and fuel composition, the appropriate engine oil can also reduce the LSPI effect.


However, the trend towards downsizing and cost saving remains fundamental. Which means a smaller quantity of oil is required. While engine or oil circuit developers would prefer somewhat more oil, the reduction of the oil quantity is irreversible from both an ecological and economical point of view.


Today, every single gram counts in vehicle design so that the ever more stringent emission requirements can be fulfilled. One litre of oil means around one kilogram more weight to be moved. And a first-fill quantity reduced by 0.3 litres adds up to a significant cost reduction when extrapolated to the mass of vehicles produced.


By the way: what is valid for the engine is applicable for the gearbox analogously.


“The bottom line is that we are experiencing a clear reduction in volume, but at the same time a higher thermal and chemical stress on the oil,” summarised Jonas.


Increasing development expenditure Accordingly, the specifications which the lubricant has to fulfil are being adapted by the car manufacturers. The engine and gearbox requirements play just as much a role as the different driving profiles and oil change intervals.


The fuels used also affect the performance characteristics of the oil. Since car manufacturers like General Motors do business all over the world, the oils must be suitable for the fuel variants used in all the different countries and on the different continents. And these can differ significantly, such as in their share of bio-components, whereby the fuels have a greater influence on oil aging than on engine development. The more biodiesel diesel contains, the faster the oil will age.


“dexos™”


”, GM specifies which test requirements the lubricant formulators have to fulfil to be granted special approval of their engine oils for GM models. “dexos1TM refers exclusively to gasoline, “dexos2TM


” ” mainly to diesel 10


What sounds like a Greek Mediterranean island is anything but a leisure activity. With the two specifications “dexos1TM and “dexos2TM


” LINK Hans-Henning Manz manz@brennstoffspiegel.de


engines, but does cover the tests for petrol engines as well. These are test methods developed by GM which have to be run through in addition to the standard industrial tests (ACEA, ILSAC) in order to determine the behaviour of the oils in the engine. The extended and revised test requirements for “dexos2TM


” are to be published in 2016. All vehicle


manufacturers develop such in-house tests specially matched to their own engines.


“Communication with the lubricant and additive manufacturers works well. We specify the limits, they test the specifications, prepare the formulation for their products and present these to us,” said Jonas, describing the usual process.


In order to reduce expenditure, the lubricant companies try to meet as many specifications from different OEMs (Original Equipment Manufacturers) as possible at the same time with the same oil. In justified cases, it is also possible to lower the costs by read across – in other words consideration of the substance groups of oils with comparable tribological and physical-chemical properties.


“As OEMs we do not dictate to the formulators which components to use. What is crucial is the result – the achievement of the required specifications,” Jonas emphasised. Experience shows, however, that higher grade base oils from Group II upwards are being used more and more often. The disadvantage: these are increasingly ‘more nonpolar’ in terms of chemical structure, whereas additives have a ‘polar’ structure. A fact which impairs the solubility of the additives in the base oil. This in turn is driving the brainstorming process for new base oil qualities.


Conclusion: Requirements on oils will continue to increase in the future due to increasingly sophisticated and optimised engine technology and after-treatment systems. Since tiny details are becoming increasingly important, the tests and tasks for lubricant formulators are becoming increasingly complex. Not only in Germany and Europe but on the global market where the lubricant companies do business. At the end of the day, everyone has the same physical phenomena to contend with.


Jonas Leber: “We are experiencing a clear reduction in volume, but at the same time a higher thermal and chemical stress on the oil.”


Thomas Hickl: “The oil has to reach every corner of the engine even under unfavourable operating conditions.”


LUBE MAGAZINE NO.134 AUGUST 2016


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