Electric Vehicle Lubricant and Fluid Testing

Electric Vehicle (EV) powertrain has fewer moving parts, incorporates different materials, and operates under conditions that are, in many ways, different than those of ICE vehicles.   Developing and testing lubricants and fluids engineered to meet the specific requirements for electric vehicles are critical to providing protection and assurance. The lubrication and cooling demands of electrical systems present new challenges to fluid formulations, primarily copper corrosion and the potential for conductive deposit formation in EV powertrains. Following are some additional fluid properties that are of concern:

• Copper compatibility. Fluids in contact with electric motors should not corrode copper windings.
• Load-carrying ability. Electric motors produce very high torque, which stresses gears in new ways.
• Aeration/foaming. The trend is toward higher-speed electric motors (even higher than 10,000-15,000 rpm), which could lead to air entrainment in the fluid.
• Electrical conductivity. There is a limit to how conductive the fluid can be without causing problems with electrical components. On the other hand, if the conductivity is too low, static electricity build-up could be a concern.
• Thermal conductivity. Fluids with higher thermal conductivity would keep the motor and drive system running cool, but oils are intrinsically poor heat conductors.
• Viscosity and friction. Any reduction in friction can extend the battery life and range of an EV.¹

Different  EV drivetrain formulations may have inherently varying corrosion rates producing conducting layer deposits in both solution and vapor phases. Conductive deposits form from the chemical reaction of the lubricating fluid and the copper at elevated temperatures under low voltage electrified conditions both in the fluid and at the vapor state.  Of concern are corrosion, deposits, and conductive deposits.

The evolution of fully electric and hybrid transportation continues to evolve and the same is true with the test methods and equipment for those critical areas of interest.  

The Wire Corrosion Test (WCT), originally developed by Lubrizol, is a new test offered by Savant Labs. In agreement with The Lubrizol Corporation, Savant Labs are the sole source for this testing service in North America.   

The WCT identifies corrosion and depletion of copper on a test wire in both fluid and vapor state. The WCT concept is to evaluate chemical reactions forming corrosion at temperatures compatible to actual performance. Oxidation and the ensuing chemical reaction on the copper wire can cause depletion of the motor winding in the EV powertrain. A sensitive wire resistance measurement method is utilized to provide a real-time assessment of copper loss due to corrosion. This test provides formulators a direct, quantitative measurement of this important attribute as opposed to current methods that attempt to infer this from visual inspection or copper concentrations in solution.

In addition, Conductive Deposit Test (CDT), equipment developed by Tannas Co., is now also available.

CDT is a unique test in that it identifies the formation of conductive bridging between tightly spaced conductors under an applied voltage. CDT emulates conditions where you have multiple conductors in close proximity in contact with lubricating fluids under potentially restricted flow conditions or condensed vapors. Motor windings are a good example.

The CDT and WCT tests are available at Savant Labs.  Please contact us for a quote. 

SAE J3200 Electric Drivetrain Fluids (EDF)

While there are currently no finalized standards for electric drivetrain fluids, the SAE instruction document (SAE J3200) published in October of 2022 focuses on thermal and electrical conductivity, oxidation, and copper corrosion. This report will assist those concerned with lubricants used in drivetrain components powered by electrified vehicles and will become a classification that specification setting organizations can utilize for their recommended practices. 

Below is a list of tests Savant can perform that may be useful for hybrid and electric vehicle applications.

ASTM International Method

• ASTM D92  Flash and Fire Points by Cleveland Open Cup
• ASTM D97  Pour Point
• ASTM D130  Copper Strip Corrosion
• ASTM D217  Cone Penetration
• ASTM D445  Viscosity, Kinematic at 100°C
• ASTM D664  Acid Number 
• ASTM D665  Rust Prevention 4 Hours (Method A or B)
• ASTM D665  Rust Prevention 24 Hours (Method A or B)
• ASTM D877  Dielectric Breakdown Voltage
• ASTM D892  Foaming Characteristics of Lubricating Oils
• ASTM D924  Dissipation/Power Factor
• ASTM D1177  Freeze Point
• ASTM D1331  Surface Tension
• ASTM D2270  Viscosity Index (Includes D445 at 40°C and 100°C)
• ASTM D2596  Four-Ball Extreme Pressure 
• ASTM D2624  Electrical Conductivity of Aviation and Distillate Fuels
• ASTM D2717  Thermal Conductivity - Single Temperature
• ASTM D2983  Brookfield Viscosity, +20°C to -60°C (Per Temperature)
• ASTM D3336  High-Temperature Bearing Performance Up to 600 Hours
• ASTM D3427  Air Release, Gas Bubble Separation
• ASTM D4048  Copper Strip Corrosion, Grease
• ASTM D4052  Specific Gravity (Includes API Gravity)
• ASTM D4683  High-Temperature High Shear / TBS Viscosity at 150°C
• ASTM D4684  TP-1 MRV Viscosity
• ASTM D4951  Elemental Analysis by Inductively Coupled Plasma, Wear Metals
• ASTM D5182  FZG Gear Test - Up to 12 and 14 Stages
• ASTM D5185  Elemental Analysis by Inductively Coupled Plasma
• ASTM D5293  Cold Cranking Simulator
• ASTM D6082  Foaming, Sequence IV (Specify Option A if Required)
• ASTM D6138  Corrosion-Preventive, Dynamic Wet Conditions (Emcor Test)
• ASTM D6304  Water by Karl Fischer
• ASTM D6417  Simulated Distillation by Gas Chromatography
• ASTM D6443  Chlorine by XRF  
• ASTM E1269  Specific Heat Capacity by Differential Scanning Calorimetry
• CEC L-45-99  mod. & D445  KRL Shear 20 Hours + 1 Temperature pre & post Shear KV
• CEC L-48 Oxidation Stability of Lubricating Oils by Artificial Aging
• DIN 51805  Flow Pressure, Kesternich Method
• SAVLAB EV-CDT Conductive Deposit Test
• SAVLAB EV-WCT Wire Corrosion Test

Grease for EV Gears and Bearings

 The e-motor in the delivery of power within the drivetrain provides full torque from the start and maintains it over a wide range of speeds. High torque and low-speed combinations place additional stress on drivetrain components, like gears and bearings. ASTM International’s committee on petroleum products, liquid fuels, and lubricants (D02) already has many lubricant-related standards in place that can be adapted to the electric vehicle market and spur its future growth.  

ASTM International Method

ASTM D217     Cone Penetration
ASTM D1264   Water Washout (Single Temperature)
ASTM D1478   Low-Temperature Torque - Grease
ASTM D1742   Oil Separation, Storage of Greases
ASTM D1831    Roll Stability of Grease
ASTM D2265   Dropping Point
ASTM D2266   Four-Ball Wear Grease
ASTM D2596   Four-Ball Extreme Pressure Up to 400 kg.
ASTM D2596   Four-Ball Extreme Pressure Above 400 kg.
ASTM D3336   High-Temperature Bearing Performance
ASTM D4170    Fretting Wear, Grease
ASTM D4289   Elastomer Compatibility NBR L and CR Grease
ASTM D4289   Elastomer Compatibility NBR L or CR Grease
ASTM D4693   Low-Temperature Torque, Grease
ASTM D5706   Extreme Pressure, High-Frequency, Linear Oscillation, SRV
ASTM D6138   Corrosion-Preventive, Dynamic Wet Conditions (Emcor Test)
ASTM D6184   Oil Separation from Lubricating Grease
ASTM D7594   Fretting Wear, High Hertzian Contact, High-Frequency, Linear-Oscillation, SRV

As leaders in lubrication testing and research, Savant Labs can help you prepare for the future as you develop fluids that meet the expanding EV industry requirements. Contact us. 

¹ Society of Tribologists and Lubrication Engineers - STLE, Cover Story, August 2021