EV Lubes Make an Entrance

In March Petronas Lubricants International launched three products: a battery coolant, a transmission fluid and a bearing grease. In May, Shell announced a line of thermal fluids, transmission fluids and greases for BEVs.

All of these companies described their EV products as meeting performance requirements specific to hybrid EVs or BEVs. Motul, for example, said its engine oils are formulated to address the start-stop cycles experienced by internal combustion engines in mild and plug-in hybrids. Fluids for integrated hybrid motors must serve dual roles – lubricating roller bearings that move at very high speeds and provide a high rate of heat exchange, while also providing lubrication and friction performance for the transmission. Moreover, these fluids need several other characteristics that distinguish them from products in ICE vehicles: compatibility with copper coiling and polymer coating and ability to withstand electrical currents.

“The formulation equilibrium to manage all these performances requirements is met by balancing all the components in the formulation,” said Francois-Jacques Benard, prospective and innovation manager at Total Lubricants. “The friction characteristics of the lubricant for excellent gearbox performance must be very precisely controlled, and as such the formulation must initially be designed like that of a standard transmission lubricant but with very precise selection of the formulation components and their relative treat rates. Additional specific additives are also included in order to achieve all the additional performance requirements for the e-engine.”

Battery fluids must dissipate the large amounts of heat generated by EV batteries. Total described formulation as a compromise between that task, providing the necessary electrical properties, protecting against fire and resistance to aging. Reducer gear lubricants are quite distinctive from products used in ICE vehicles because these gears can reach speeds above 15,000 revolutions per minute. This requires superior anti-foaming and air-release properties that must be sustained for the service life of the fluid.

Total said its multipurpose BEV fluids again must serve multiple roles, lubricating reducer gears, lubricating the electric motor and cooling the battery and power unit.

“Therefore they must first protect against electrical shorts and static electrical discharge,” Benard said in an email exchange with Lubes’n’Greases. “Second, protect against fire propagation in case of thermal runaway in the battery cells; third, provide optimal heat exchange even during fast charging; fourth, protect against fire in case of an accident; fifth, ensure compatibility with the copper coil and its polymer coatings; sixth, ensure durability of gears and rolling bearings at low and high speeds; and seventh, prevent foaming and aeration.

“All of that performance must be achieved and maintained through the entire service life of the fluid. None of the current lubricants used in ICE vehicles are able to provide such a broad range of performance. Therefore, once again, all the components from the base oils to the additives have to be carefully selected and balanced to achieve the performance necessary, ensure the energy efficiency of the vehicle and ensure that it runs trouble free.”

Some companies said it is not necessary to develop fluids for hybrid transmissions that are not integrated with electric motors or for ICE motors in hybrids because their performance requirements are similar to hardware in vehicles powered only by ICEs.

Total said it worked two years to develop its EV slate, which includes products marketed under the Quartz brand for light-duty vehicles and the Rubia brand for industrial and utility vehicles and electric buses.

Lubricant marketers agreed that sales of EV fluids are mostly going to factory fill and that this will continue at least for a few years.

“Several of the products in the Quartz range are optimized for the next generation of EVs,” Benard said. “Most of these fluids may have long drain intervals – perhaps five years or more – so at least for a few years the market will remain focused on factory fill, with aftermarket volumes increasing as a function of drain intervals. Our marketing will therefore remain focused on engine and vehicle designers as it is currently for the ICE factory fill market.”

Sources gave several reasons that more companies have not introduced lubricants for EVs. First, potential sales volumes are still low. Although their numbers are growing fast, EVs still accounted for less than 3% of global vehicles sales in 2018, and they offer far less opportunity than ICE vehicles for aftermarket replacement business.

It also appears that automakers have not made a priority of using products designed specifically for EVs. Sagawa Takumaru, manager at Nissan Motor Co., said the company has to date used lubricants from ICEs in its Leaf, which for years has been one of the top-selling BEVs. 

“Unique lubricants are usually expensive,” he said in an email exchange, referring to products designed for new applications. “So to reduce costs, we are adopting the same lubricants as for ICE vehicles.”

Nissan uses a water jacket – rather than a lubricant – to cool the Leaf’s electric motor, an automatic transmission fluid for its reduction gear and does not yet use battery coolants. “In the future, cooling will become more important, so we are considering which fluid is the best,” he said. As for the Leaf’s lubrication needs, “If a new fluid achieves better efficiency, better cooling or cheaper cost, we will consider them. If not, we will keep the current ICE lubricants.”

Industry insiders said the products being used in existing EVs generally appear to perform adequately but that it is premature to reach definite conclusions. EV manufacturers have encountered a few problems related to lubrication, they said – bearing wear in at least one model, lubricant foaming in another. A representative of one automotive equipment manufacturer said the majority of EVs have not been in use long enough to know whether they are wearing prematurely.

There is consensus that future EVs will have greater needs for specifically developed fluids. For example, as part of their push to extend driving ranges, OEMs are already planning to employ bigger batteries, which will generate far higher amounts of heat and require far more cooling.

But OEMs are also waiting to see if new fluids can provide performance that distinguishes them.

“It will come down to whether they can enable performance,” Arup Gangopadhyay, technology leader for lubrication science and mechanical friction in Ford Motor Co.’s base engine department, said on the sidelines of a May 20 forum about EVs at the annual meeting of the Society of Tribology and Lubrication Engineering. “For example, when they can demonstrate enough heat dissipation performance to allow a smaller gearbox, then we will use that product.”

All agree that designs of PHEVs and BEVs continue to evolve and are doing so quickly. It appears that future models will have lubrication and cooling needs that further differ from ICE vehicles. That and a growing EV population should certainly lead to introduction of more fluids and lubricants formulated specifically for those vehicles.