November 01, 2020

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Is low viscosity and long drain the key to the industry's future?

low-viscosity lubricants

By Blaine Denton

With the ever-increasing demand for lower emissions, there has been a marked pursuit of new solutions. “Manufacturers are feeling the pressure to meet legislative targets and avoid fiscal penalties. There is also a strong customer desire for cars that are more efficient, both in terms of the impact on the environment – and their wallets,” says Richard Egan, head of technology at Castrol Professional, based in Pangbourne, U.K. Castrol Professional, a sub-brand of Castrol, which is owned by BP, focuses on Castrol’s business-to- business (B2B) automotive business.

“When we look out to the future, we essentially see the convergence of two intertwined themes: increased demand for energy due to population and GDP growth, coupled with the need for energy-efficient solutions that help reduce GHG emissions and ease overall energy demand,” says Brad Rinderknecht, synthetics global marketing manager for ExxonMobil Chemical Co.

“Addressing these trends will require engine lubricants to evolve to meet a number of challenges. Innovations in engine and equipment design have helped further energy efficiency gains and have helped meet emissions-reduction requirements. However, to sustain or accelerate efficiency improvements, further advancements must be made to develop lubricants that help achieve even greater fuel economy and energy efficiency, longer drain intervals, and the ability to perform in increasingly severe operating conditions,” he adds.

LOW VISCOSITY AS A SOLUTION?

Lubricants, particularly low-viscosity lubricants, are just one of the enablers to achieving better fuel economy and reduced vehicle emissions. In December, we surveyed industry experts on low-viscosity lubricants and long drain and whether they see these as the key to the industry’s future. The experts appeared divided on the subject

In fact, Ian Bell, the U.K.-based technical director at global additive manufacturer Afton Chemical, believes that low-viscosity lubricants will only play a minor part in the industry’s future. “To truly access new levels of emissions and fuel economy performance, lubricants need to take into account far more than just lowering viscosity,” he says. To maximise the potential benefits, one would ideally see the lubricant and the engine hardware developed in parallel, he adds. “The future of the industry will be in delivering value and enabling emissions reductions/fuel economy, and delivering that will be a multifaceted challenge.”

For Lutz Lindemann, board member of lubricant manufacturer Fuchs AG in Mannheim, Germany, low-viscosity technology is “one major trend in our industry” and “low-viscosity oils can make a modest but important contribution” to both fuel economy improvement and CO2 reduction.

While these statements appear to represent opposing views, Lindemann touches on the commonality between them. “The driver in all developments is fuel/energy efficiency and sustainability requirements in engines, generally in all tribological systems. Therefore, the trend towards low-vis applications is a consequence out of these requirements.”

LOOKING DEEPER INTO DURABILITY

While there’s no doubt that low-viscosity lubricants are helping improve vehicle fuel economy and reduce vehicle emissions, the real questions are: to what degree and at what cost? In general, it is desirable to have the lowest possible viscosity lubricant so long as it can still protect the two moving surfaces from wear. If viscosity is too high, energy is wasted within the system as the parts struggle to move against the lubricant. Too low, and the moving parts can come into contact, causing friction and wear.

While OEMs are using all of the tools they have to reduce CO2 emissions, this is only viable with low-viscosity oils if the hardware is well protected from wear and tear, says Shell Helix Technology Manager Robert Sutherland. “This means there will need to be a balance between drain interval, durability and CO2 reduction, based on the lubricant choice made by the OEM.”

Engine wear protection provided by low-viscosity oils is a major concern for OEMs, says Simon Tung, global OEM manager, Vanderbilt Chemicals, headquartered in Norwalk, Conn., U.S.A. “Lower viscosity grade oils might not be able to have enough oil film thickness to protect engine wear like higher viscosity grade oils. Due to this concern, low-viscosity grade engine oils, such as SAE 0W-20, are not common in tropical climates, though they could provide the added benefit for fuel economy. In addition, engine durability is still the highest priority for OEMs. Even with the fuel economy benefits derived from low-viscosity lubricants, OEMs still believe that this low-viscosity lubricant can lead to accelerated wear and result in seizure of the engine crankshaft. OEMs don’t want low-viscosity lubricants to sacrifice engine durability.”

The importance of durability is also emphasized by Mark Sztenderowicz, global manager, automotive engine oil product development for Chevron Oronite, especially in the commercial sector, where “the migration to low-viscosity oils will be tempered by the imperative of reliability and durability.” While operators are motivated to save operating costs, they also want to be assured that engine life and up-time will not suffer, he says.

THE REASONS WHY LOW VISCOSITY IS TRENDING

Perhaps one of the main reasons for the popularity of low-viscosity lubricants is that “to date the largest ‘lever’ a formulator has had at his disposal has been to reduce the viscosity of the fluid,” says Bell. Other solutions, such as additive effects, “are around an order of magnitude smaller than the benefits via viscosity grade changes,” he says.

This is true for a number of reasons. One of the primary mechanisms of action by which additives increase fuel efficiency is through the use of friction modifiers, molecules that contain a polar group that can attach to metals, and a lipophilic group that provides oil solubility in addition to a cushioning effect. Although the degree to which friction modifiers can increase fuel efficiency is dependent upon the specific type in use, some studies have found fuel economy improvements of 0.27%. In comparison, lubricants with lower viscosity have been shown to provide up to 8% improvement in benchmark tests, under certain conditions.

FURTHER FACTORS TO CONSIDER

One important consideration in this discussion is the fact that not all engines respond well to low viscosity lubricants. In fact, some engines experience worse fuel economy with lower viscosity fluids. In short, it is important that a holistic approach is adopted and that factors, such as engine hardware, are considered alongside the lubricants. Although given that the average age of cars has steadily increased from 8.4 years in 1995 to 11.4 in 2014, OEMs must carefully consider the ease with which any solution can be adopted. New technological developments take long before they are widely adopted. As such, low-viscosity lubricants are (in a limited way) effective, and they are easy to roll out to the public.

Mohd Khalid Bin Mohamed Latiff, head, group strategic planning and M&A for PETRONAS Lubricants International (PLI), believes that the adoption of low-viscosity lubricants will continue “as higher quality base oils become more accessible for lubricant suppliers.” He points out that while “conventional/ mineral lubricants are expected to globally grow in volume at just over 2% per annum till the end of the decade, synthetic lubricants [which enable the formulation of low-viscosity oils] are expected to grow at a rate above 5% during the same period.”

Elaborating on his earlier point, Bell explains that, “Reducing lubricant viscosity has been, and will continue to be, an important aspect of delivering emission and fuel economy benefits to OEMs and end users. However, it is not the only important consideration. And as we look to the future we will see an ever more complex challenge requiring ever more sophisticated solutions.” Downsizing, gasoline direction injection (GDI), reduced sump size and extreme turbocharging are some of the options that OEMs are exploring. While those options are effective in their own ways, they do fall short of low-viscosity lubricants in one important aspect: ease of adoption.

LONG-DRAIN INTERVALS

Another potential solution to this issue is to extend oil drain intervals. According to Bell, “Extending oil drains is a real benefit to end users and could have a tangible impact on environmental impact via reduced fluid consumption, but in comparison to other design criteria, such as fuel economy performance, the impact is small.”

And while longer drain intervals could have significant impact on fuel economy and consumer convenience, there are a few mitigating factors. Oil quality and engine cleanliness both contribute to the viability of long-drain intervals in the sense that contaminants can damage engines without proper cleaning or filtration. As Sztenderowicz points out, “long drain will continue to grow, but only to the degree where equipment life and up-time is not adversely affected.” Furthermore, long-drain intervals have another fringe benefit. Longer drain intervals offer convenience and lower costs.

CHALLENGES FOR THE FUTURE

However, Tung, formerly of General Motors R&D, points out that there are doubts whether low-viscosity oils can meet both future fuel economy and long-drain requirements.

“These two seemingly discordant performance requirements, with profound implications on modern engine oil formulations, must be changed to cope with fuel economy and green environmental needs,” he says. “To address these global concerns, additive companies must team together with OEMs to develop a unique formulation approach to improve fuel economy, reduce greenhouse emissions and maintain emission system compatibility. At the same time, oil oxidation resistance, wear protection and anti-corrosion performance should not be compromised.”

Consumers have a big role to play in terms of long-drain intervals. “Oil drain intervals are still decided by the consumer, several of whom disregard the OLM [oil life monitor] and will change their oil an average of 4,700 to 5,700 miles based on odometer readings,” says Mike Brown, vice president of technology, SK Lubricants Americas.

Japanese engine manufacturer Honda is at the head of the drive for lower viscosity lubricants, points out Jonathan C. Evans, vice president, technical development at Midland, Mich., U.S.A.-based Savant Group. Honda is currently using a 0W-8 viscosity grade oil in seven of its vehicles being sold in Japan. “These oils are expected to deliver even better fuel economy and will undoubtedly over time find their way into the global marketplace as OEMs are pressed to meet the new United States fuel economy targets of 2025.”

Both Brown and Ernie Henderson, president of K&E Petroleum Consulting, LLC based in Oklahoma City, Okla., U.S.A., see the trend towards low-viscosity oils accelerating.

“SAE International updated the J300 Engine Oil Viscosity Standard in April 2013 with the addition of SAE 16, thus extending the global standard to low-viscosity engine oils. Soon, another J300 update will be available for SAE 12 (2.0 cP minimum) and SAE 8 (1.7 cP minimum). This global standard provides a common oil viscosity framework, thus enabling engine designers to chase more fuel economy with lower friction engines. We expect the appearance of SAE 0W-16 and SAE 0W-8 engine oils in consumer market channels following their SAE grade recommendations in vehicle owner manuals,” Brown says.

“In terms of base oils, the average base oil quality that would be required to produce the complete profile of PCMO (i.e. low and high engine oils) in North America will have changed from approximately 6.5 cSt @ 100°C and 97.5 VI in 1985 to 5.0 cSt @ 100°C and 111.5 VI by 2015. This highlights the continuing change to the use of lower-viscosity and higher VI base oils,” Henderson says. He adds that, “Each of these changes requires a careful balance of premium base oils and an advanced additive system.”

Although there is hardly a conclusive answer whether low-viscosity lubricant or long-drain intervals will be the primary industry drivers, it is clear that what they have in common will be just as important. Namely, both strategies are easily implemented, cost effective and do not significantly inconvenience the consumer.

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