The changing landscape of E-vehicle lubricants

Dr. Raj Shah, Dr. Mathias Woydt, Ms. Hillary Wong and Mr. Isaac Kim, Koehler Instrument Company, Inc.

The last decade has seen a dramatic increase in the development of electric vehicles (EVs), essential for the reduction of carbon dioxide (CO2

) emissions.

On April 17, 2019, the European Union adopted Regulation (EU) 2019/631 adding new CO2


targets to reduce emissions in cars by 15% from 2025 and 37.5% from 2030, with respect to 2021 starting points. The most important benefit that can be attributed to this regulation is the incentivisation of zero-/low-emission vehicles (ZLEV) defined as a passenger car or van with CO2

gr.CO2/km. According to the European Automobile

Manufacturers Association (ACEA), in 2020, hybrid electric vehicles (HEV) reached a market share of 11.9% of total passenger car sales across the EU and electrically chargeable vehicles (ECV) achieved a similar level of 10.5% as seen in Figure 1. This is a clear increase from the market share of 3% in 2019, but the overall market declined by 3 million units in car registrations and the demand was boosted by stimulus packages.

As OEMs each have their own unique electric motor designs, creating lubricants for EVs is a difficult endeavor requiring a specific lubricant to fit their needs for performance and friction reduction, especially since EV lubricants have greater technical requirements compared to conventional ICE lubricants. EV lubricants must improve on anti-wear performance, friction reduction and efficiency, in conjunction with compatibility to arcing and insulation and electric motor, inverter and battery pack cooling. EVs require lubricants in vital electrical components such as coolants for the car battery, gear oils for differentials, chassis, gear reducer and wheels, brake fluids, and grease for other components of the EV.

Figure 1: Market share of new cars by fuel types in 2020

Despite the promising potential and growth of electric vehicles, researchers have encountered the same issues experienced with internal combustion engine (ICE) vehicles: performance optimisation. As


Efficiency is an important area of focus and correlates directly to the torque properties of EVs and range. Since electric motors are designed to be compact to save weight and space, higher rotational speeds of up to 18,000 rpm are expected. When there is high stress in the electric motor, air can infiltrate components and cause fluids to foam, causing damage to the components’ surfaces. Reducing torque through the development of low viscosity lubricants will help solve those issues and push EVs to dominate the automobile industry. However, the formulated greases must refrain from altering mechanical properties such as tensile strength and crack resistance which requires many trial tests to balance the properties.

emissions within 0-50

the automobile industry is making progress towards a new age of EVs, a new set of fluids, lubricants and oils must be specifically tailored to the performance requirements of electrical and gear components in EVs. Tribological performance testing for EVs are conducted to evaluate and further understand the characteristics of these advanced lubricants. The goal of EV lubricants is to minimise friction loss, enhance durability, bolster efficiency, and strengthen other performance aspects paving the way towards a greener future.

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