Electric Vehicles

EVs and Their Fluids
A Mercedes-Benz E300, a later incarnation of a series of vehicles born in 1953. © Mercedes-Benz AG

EVs and Their Fluids

By Simon Johns - Sep 15, 2023

Electric vehicles are continuing to grab market share of new vehicle sales, despite global economic uncertainty. Even though sales of EVs are increasing exponentially around the world – over a still-small base – they have had little impact on lubricant formulations to date. Will this change? Opinion is divided.

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, a handful of companies have introduced lubricants marketed specifically for electrified passenger cars. They include Total, Motul, Petronas, Shell, ExxonMobil, Fuchs, Castrol and Valvoline, among others.

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.

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.

There is an important distinction to be made between hybrids and battery electrics and hydrogen fuel cell vehicles. Hybrids have all the lubrication requirements of an ICE, and not only have an electric motor that needs lubrication but the e-motor also gives rise to more severe operating conditions that the lubricant must tolerate.

The need for conventional engine oils is eliminated in battery EVs altogether, but they still require numerous types of fluids and greases. The two main ones are some kind of thermal management fluid for the battery and a transmission fluid for the e-axle and/or electric motors that can be either dry or wet depending on the model of car.

In the case of hybrid lubricants, while they have performance requirements in common with those of conventional vehicles there is as yet no specific standard for hybrid lubricants. There is a general push toward lighter viscosities to help maximize efficiency, and antiwear and detergency remain important parameters.

Lower engine running temperatures in a hybrid’s ICE when running mostly on battery power 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. 

Electric motors and the batteries that power them – especially upcoming generations of batteries, which will be have ever-greater energy density – 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 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.

Related Topics

Electric Vehicles    Finished Lubricants    

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