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The combination of increased biofuel content and the regeneration strategies employed to maintain the effectiveness of diesel particulate filters (DPF) can lead to an increased presence of biodiesel in the engine sump. This raises concerns in terms of piston cleanliness, oxidation stability, cold starting and corrosion. As a result, a number of tests have been introduced into industry specifications to monitor the performance of the lubricant in the presence of biodiesel.
If the volume of biodiesel blended with conventional diesel continues to rise, I believe it will be increasingly important to use high quality lubricants tailored for these applications to meet performance and protection requirements.
Base oil evolution OEM requirements for improved performance and aftertreatment protection mean we can expect an increase in the use of higher quality base stocks. The higher saturates and lower sulphur content of Group II and III compared with Group I can help to deliver improved oxidation, better deposit control and enhanced catalyst compatibility.
In addition, the increasing content of lighter cuts used to formulate thinner viscosity grades can help to improve fuel economy. Properties outside of the API classification of base oil groups can also provide strong benefits. For example, the increased NOACK volatility and better low temperature performance provided as we move from Group I and Group II to Group III are equally important to formulate fuel efficient lubricants and bring an opportunity for base oil differentiation. One question that needs exploring is whether there will be enough good, high performing base stocks to meet growing European demand.
Euro VI trucks and fuel economy The Euro VI emissions standard does not include any CO2 restrictions, which means it provides no incentive for fuel economy improvement. But, because the cost of fuel represents about 25 to 30% of the total operating cost of a truck, it is high on the agenda of OEMs and fleet owners. We have already seen a significant reduction in fuel consumption, a trend we can expect to continue.
One enabler for reduced fuel consumption is the use of lower viscosity lubricants. In testing it has been demonstrated that moving from SAE 15W-40 to SAE 10W-30 or 5W-30 can deliver significant fuel economy benefits. This has led some OEMs, for example MAN and Scania, to develop specifications that only allow SAE xW-30 grades, while Iveco has introduced lower HTHSV lubricants.
To support the trend towards more fuel efficient lubricants, ACEA will introduce ‘F’ Sequences with an HTHS requirement of 2.9 – 3.2 cP in the future.
It is essential that these thinner grades deliver robust low temperature pumpability performance to reduce the risk of engine wear.
To date, most of the EMEA Group II requirements have been met through imports. However, further announcements will help to change this ‘unbalanced’ picture. For example, ExxonMobil has confirmed a new Group II plant in Rotterdam, which will start up in late 2018. In addition, Luberef and Rosneft have announced plans to bring additional Group II on stream in 2017.
So far, outside of any unusual supply disruption, there has been sufficient production of Group III base stock in Europe to meet local demand. Here again though, we can expect some supply increase as new players, such as ADNOC and Tafneft, join established suppliers including SK, Neste, S-Oil, Petronas and Shell.
Conclusions The introduction of the stringent Euro VI emissions standard has pushed OEMs to revise their aftertreatment strategies. At the same time, as end users look for ways to reduce their operational costs, OEMs are looking for fuel economy improvements. It is increasingly important to formulate Euro VI heavy-duty diesel lubricants using higher quality, Group II and III, base stocks to ensure they can deliver against both of these requirements.
LINK
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LUBE MAGAZINE NO.139 JUNE 2017
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