Since the Industrial Revolution, air pollution has been an item of concern for residents of countries around the world. In England, for example, people have been fighting the problem since 1956, when the government passed the Clean Air Act of 1956. The most recent action was taken in 2008, when the Climate Change Act was passed. The goal of that legislation is to lower overall greenhouse gas emissions from all sources of energy production.
Obviously, the fight didn’t just take place in England. The US has its own long history of battling air pollution. In fact, Congress passed the Air Pollution Control Act in 1955, one year before the UK passed its first legislation. In 1970, the US passed the Clean Air Act, the landmark legislation that has helped make the air cleaner for millions of US citizens and continues to work toward that goal more than 40 years later.
But the effects of climate change have made the fight even more intense in the last decade than ever before. More people are seriously investigating the possibility of purchasing an electrical vehicle (EV) instead of vehicles with internal combustion engines (ICE). The goal is to eliminate (eventually) the need for traditional fossil fuels to power ICE vehicles, reducing the transportation sector’s carbon footprint and supporting the climate change fight.
Consequently, lubricant manufacturers are beginning to adapt their greases so they can be used in EVs and hybrid EVs (HEVs). It is important to examine the current state of vehicle lubrication and how its adaptation to EVs and HEVs will alter the way greases are manufactured and used.
The wild card for the lubricant market is what is going to happen as more vehicles become electrified
What exists now
Currently, there can be more than 50 different kinds of grease used in conventional ICE vehicles, and that market has remained strong for decades. In 2019, the most recent year for which data exists, 483,000 metric tons of grease were sold worldwide. There are four reasons that vehicle manufacturers use greases in their vehicles: corrosion-protection, lubrication, water-resistance and antisqueak. When greases are deployed inside the passenger compartment, they are most often used for light lubrication applications like noise reduction. To be used in the interior, they must be plastic-compatible and last as long as the components do. On the outside of the vehicle, manufacturers use greases in antiwear, anticorrosion and antioxidant applications.
Naturally, the most frequent uses for grease include steering racks, suspension joints of light trucks, door hinges, locks and handles, brake mechanisms, shock absorbers and wheel bearings, among others. But specialty greases are often used in small volumes of electrical contact switches, pedal mechanisms, accessory drive bearings, seat adjusters, window winders and other applications.
Potential changes with electrification
In most cases, the greases on HEVs will not look that much different from the greases currently used on ICE vehicles, with the notable exception of starter-motor greases. They will no longer require high shock-load resistance because starter-motors in stop-start vehicles act as a generator when they are not restarting the engine. Additionally, transmission electric motor bearings may be grease- or oil-lubricated if they are engineered into the gearbox.
Unlike traditional ICE or HEV motors, EV motors have different grease needs. Instead of being used for the traditional reasons, greases in EVs must exhibit the following attributes: long life, low noise, conductivity or insulation, energy efficient. To reduce the drain on the vehicle’s batteries, the energy efficiency and life span are paramount considerations for greases that are going into EVs.
While there are more than 50 grease applications on a typical ICE vehicle, energy efficiency only matters in four specific applications: drivetrain joints and bearings, front-end accessory drive bearings, wheel bearings and steering mechanisms.
The duty cycles of vehicles present the most pressing challenges for its energy efficiency. After all, good lubrication films are not generated at low speeds. Energy losses occur when in-boundary lubrication is used, and, while thicker base oils improve on the film thickness at lower speeds, it contributes to higher speed churning losses. In contrast, higher speeds produce thicker lubrication films. The use of lower-viscosity oils will allow for thinner films to form, which will therefore prevent churning losses—but, as discussed, if the resulting films are too thin, it will compromise the durability of the components.
As the electrification of the transportation sector continues apace, it is important to make sure the lubricant market has adapted to the new requirements of EV
What the future holds
Over the next several years, most lubricant manufacturers believe there will be little or no change in the way greases are used or formulated. As HEVs become more common, there will naturally be alterations in the greases used in starter motors and electric motor bearings.
The wild card for the lubricant market is what is going to happen as more vehicles become electrified. Greases that affect vehicle range will require higher performance in energy efficiency, durability and long life. In addition, conductivity and resistivity will also become significant factors in EV greases, but at the moment most of those concerns are vehicle hardware specific.
As the electrification of the transportation sector continues apace, it is important to make sure the lubricant market has adapted to the new requirements of EVs. The challenge before the industry is to make sure manufacturers and consumers are familiar with these specific needs and create the infrastructure to deliver them.
About the author: Gareth Fish is Technical Fellow, Industrial Additives at The Lubrizol Corp