Jul 25, 2023
Posted by Mathew Robin, Technology Manager, Consumer Engine Lubricants, Udo Roehrs, Technology Manager, Gareth Fish, PhD, DIC, BSc (Hons), ARCS, CSci, CLS, GLGS, Technical Fellow, Industrial Additives
As the hybrid and EV market continues to evolve and grow, the requirements of fuels, engine oils and lubricating greases for these vehicles are becoming clearer. Extensive research and testing have helped illustrate the biggest challenges in electrified vehicles compared to traditional Internal Combustion Engine (ICE) cars and trucks. These point the way toward the lubricant and grease formulation changes needed to support this transportation market evolution.
Market forecast for hybrid engines and electrification
Production of electric versus plug-in or other hybrid-engine vehicles varies by region of the world, but all signs show that we’ve reached a tipping point in the transition away from ICE vehicles. By 2030, over 70% of new vehicles will be electrified in some way, meaning the focus on how electrification will impact formulations is inevitably increasing.
Hybrid vehicles require lubricants formulated to address lower temperatures and more
Protecting hybrid vehicle engines starts with the understanding that these engines experience reduced operating temperatures and more start/stops than traditional ICE vehicles. This brings several challenges including the control and release of water from the engine oil, the formation of acidic white sludge, higher fuel dilution in the engine oil, and the impact of aged fuels and deposit control.
First, the lower average operating temperatures in hybrid vehicles, caused by changes to the duty cycle versus traditional ICE vehicles, results in an increased risk of water condensation and fuel dilution in tandem with reduced opportunities for evaporation. A lubricant with considered emulsification capabilities is needed to effectively manage this excess moisture. However, simply addressing the issue through high levels of emulsion stability can prove harmful. Where excess water remains in the lubricant without evaporating or separating, acidic white sludge can form leading to an increased risk of corrosion and wear. A second challenge appears when excess water that is not emulsified within the lubricant, re-enters the sump creating the potential for oil starvation. A careful balance must be reached in the formulation to ensure optimized emulsion formation and water release in hybrid engines. Fuel dilution into the engine oil will also be higher for hybrid vehicles, which leads to an increased risk of piston deposit formation, and therefore a requirement for good cleanliness control from the lubricant. Additionally, fuel tends to sit in the tanks and/or engines of hybrid vehicles, which can lead to increased corrosion and oxidation. Specially formulated fuel additives can minimize these deposits.
Electrification means changing grease needs
A lot of the components on a car or light-duty truck that require grease are the same no matter what style of engine, but some differences have surfaced in HEVs and EVs compared to ICE vehicles. For hybrid engines, starter-motor grease will no longer need to have high shock load, extreme pressure (EP) performance because the starter motor can be permanently engaged on these vehicles.
The big difference, and the greatest challenge for lubricating grease, is in the weight of HEVs and EVs compared to traditional ICE vehicles. The batteries and motors on HEVs and EVs bring the vehicle weight up 20-25 percent more than an ICE vehicle. The added weight has an impact on wheel bearings, steering mechanisms and transmission joints. Grease formulations will have to respond to this challenge.
New technology for electrified vehicles means new greases, too. Transmission electric motor bearings may be grease lubricated or oil lubricated. Electric-motor bearing greases and greases to support motor and coolant pumps that control the battery temperature in EVs also represent emerging grease needs.
What the (near) future holds
Field trials and testing continue to show the unique needs of hybrid vehicles, but we know engine life can be maximized with the right formulations. For engine oils and fuel additives that means ensuring the highest quality products are utilized and formulations are aligned to specific OEM requirements. For automotive greases, little change can be expected over the next few, but a lot of unknowns exist as HEV and EV production grows. One certainty is that standard lubricating greases will need to evolve.
For more information, contact your Lubrizol representative.