EVs and Their Fluids

Electric vehicles are continuing to make major inroads into personal mobility. Even though sales of new EVs are increasing exponentially around the world – over a still-small base – they have had little impact on lubricant formulations to date. But this could change.

Mass-produced electrified vehicles have been on the market for a couple of decades, but the development of dedicated lubricants and fluids for them is just beginning to gain momentum. Since late 2018, only a couple of companies had introduced lubricants marketed specifically for electrified passenger cars. Over the past year, several others have joined their ranks, which now include Total, Motul, Petronas, Shell, ExxonMobil, Fuchs, Castrol and Valvoline.

However, at least some original equipment manufacturers are not yet convinced that the market is providing the products that they want. Industry sources say most EVs are operating on conventional fluids developed for vehicles that employ only internal combustion engines. These sources stop short of saying that the EV lubes on the market do not offer differentiated performance, but they do maintain that they do not yet offer enough of what EVs need to warrant using them.

Most EVs are running on conventional fluids developed for ICE vehicles, leaving the lubricant industry with work to do to convince some OEMs that they are getting the products they require.

Work continues to develop the lubricants and fluids, while automakers are still evolving designs. Indeed, in some markets, such as China, the line-up of manufacturers is still very much in flux, and there is consensus that engines and drivetrains will yet undergo significant evolutions. As always, lubrication demands follow equipment design, so to some extent requirements of future EVs have not been defined.

Following is an explanation of the lubrication and cooling needs of EVs – hybrid and plug-in – and how they differ from those of conventional ICE vehicles. It begins with descriptions of various categories of EVs and their design differences from one other and conventional vehicles and then explains how those designs translate into different lube performance requirements. It also discusses some of the implications on formulation.

The need for conventional engine oils may be eliminated in BEVs, but all EVs still require numerous types of lubes, fluids and greases, especially when one considers hybrids that still contain ICEs. Many of those lubes have performance requirements in common with those of conventional vehicles. There is a general push toward lighter viscosities to help maximize efficiency, and antiwear and detergency remain important parameters. There are, however, significant differences.

Lower engine running temperatures in a hybrid’s ICE can impair the performance of antiwear and antioxidant additives that are designed to activate above a certain temperature. The fact that ICEs in full and plug-in hybrids also operate less than full-time means the oils lubricating them must also cope with increased water and fuel dilution, along with increased contamination by organic acids. EVs also use different materials for things such as sealants, creating different requirements for material compatibility. 

As the move toward greater electrification of the global vehicle parc continues – driven by tightening emissions legislation and consumer demand – engine oils will be exposed to more electrical current and operating conditions will change.

Electric motors and the batteries that power them – especially upcoming generations of batteries, which will be larger – generate so much heat that they are creating demand for coolants, which could represent a new opportunity for lubricant suppliers.

Three performance requirements are drawing much of the auto and lubricant industries’ focus at the moment: cooling, electrical conductivity and copper compatibility. The thermal management needs of the latest e-motors and batteries are already significant, but they are expected to increase as manufacturers employ even larger batteries and as charging speeds of those batteries continue to increase. Mechanisms for thermal management are still very much in a state of change, but the use of coolants to transfer heat is already one of the main approaches and is expected to remain so. Some say the industry is still searching for fluids that will be able to provide the necessary performance.

EVs operate with much higher electrical currents than conventional ICE vehicles, leading to concerns of potential problems. First, lubricants and fluids might conduct electricity too easily, resulting in current bleed that saps operational efficiency and is a physical threat to the occupants. Alternatively, fluids might insulate current, causing a static charge build-up that leads to arcing – again, a safety threat. Research over the past year has indicated that conductivity is affected by polarity of chemical additives and fluid viscosity and that it changes as fluid ages. Research in this area will continue.

EVs contain much more copper than ICE-only vehicles, much of it carrying current and some of which comes into direct contact with lubricants or coolants. Preventing that copper from corroding is of obvious importance and so has become a new parameter for EVs. Formulators researching the issue reported this year that it could require adjustments in use of additives containing chemicals such as phosphorus, boron and sulfur.

Lubricant development can be an ongoing activity even for categories of equipment that are much more established than EVs. In this case, it is clear that lubricants and fluids will be much researched and undergo much development in the coming years.

What is certain is that as we move toward greater electrification of the global vehicle parc, engine oils will be exposed to more electrical current and operating conditions will change.  

Engines aside, fluid development continues to face new challenges, from new materials used for seals or light-weighting hardware to injection systems combined with advanced electrification systems.

Fluids will also be both exposed to electric current at voltages not seen in today’s engines and be in contact with electric insulating materials. The use of electric motors will also expose fluids to magnetic fields that may also impact the fluids used in tomorrow’s vehicles. Will fluids be compatible with new materials to ensure longevity of both the fluid and the new materials, seen as critical to successful innovation? Engineers need solutions before problems develop, especially when it comes to consumer acceptance of new technology. 

Fluids’ electrical properties will have to be considered and balanced. Too much conductivity can cause leakage, which may lead to risk of shock or short circuiting of key components to the e-motor. If fluids are too effective as insulators, static charge can build up until it results in electrical discharge that can damage components in the vehicle. Either is clearly unacceptable for consumers or mechanics, and issues that cause EVs to be less reliable will delay acceptance. Properties need to be understood and defined for optimum fluid performance.

As the sale of new types of low-emission vehicles is becoming more mainstream, there is greater potential to develop and optimize bespoke lubricants for new electrified powertrains and hardware. This extends to the need for collaboration between OEMs and the lubricant industry and includes both additive suppliers and potentially improved base stock options that will allow for better heat transfer properties and longer life. There are significant examples of collaborations in the world of transmissions, where fluids are optimized for the given transmission and are designed for long life under normal driving conditions. Some OEMs may work with more than one additive company, but in many cases a single additive will emerge at least early on. These collaborations are not public information.

There are also opportunities to design fluids for e-motor and battery cooling. Similar to grease and other fluids today, EV makers are using off-the-shelf solutions that are widely available. Today, EVs are air-cooled or use glycol-water systems. Both batteries and e-motors need to be cooled to maintain efficiency and ensure long life. OEMs would like options that provide the heat transfer benefits of a glycol-water fluid, for example, but are lower in density and can last longer, reduce maintenance and potentially improve overall efficiency, which could have a positive impact on range. 

The next decade is likely to be a period of transition for the lubricant industry as innovation leads to products better suited to hybrids and BEVs, which have more complex thermal management challenges than ICE vehicles.

The 2020s will be a period of transition for the lubricant industry, as innovation leads to more products well suited to hybrids and advanced ICE designs. Meanwhile, EV manufacturers will look for more tailored solutions for their lubricant needs and will decide which fluids will play what role in e-motor and battery cooling. It is likely that the lubricant industry will also see a greater impact on demand in the next decade, emanating from extended-life products that are the result of advanced additive and base oil technology, as well as a rapid upgrade to higher-quality products in all regions of the world. 

Innovation that improves the lubricant’s thermal and electrical conductivity impacts will become important features, whether for conventional hybrids or transmissions for EVs – on top of wear, deposits and all the other critical issues that lubricants protect against. No matter what technologies win out, there is little doubt that the lubricant industry needs to be ready to meet those needs.