Transmission Fluid
Transmission Fluid – Despite increasing vehicle electrification, some OEMs still use existing lubricants to cool and protect transmissions and electric motors. Afton Chemical explores whether the demands of the latest hardware and the benefits offered by custom ETF should override the reassurance of familiar fluids.
A history of proven performance is attractive for OEMs hoping to avoid the need for dedicated electrified transmission fluid (ETF) in their supply chain. However the rapid pace of change in hybrid and electric vehicle development brings additional lubricant demands and opportunities for enhanced performance, neither of which should be overlooked.
New lubrication needs
Higher eMotor power and speeds require better cooling: fluids need the right thermal conductivity and viscosity characteristics. Direct cooling is most effective but when lubricant is in contact with eMotor components, properties not needed for ATF or MTF become relevant.
Electrical properties like fluid conductivity, resistance and breakdown voltage must be appropriate. Compatibility with sensitive materials like copper, silver, tin and plastics in eMotors and related electronics, becomes a priority – in the oil’s liquid and vapour phases.
Where dedicated hybrid transmissions (DHTs) are used, the absence of torque convertors and launch clutches results in higher power transfer across gears and bearings, increasing the risk of wear.
As well as efficiency, OEMs seek extended drain intervals – up to 250,000 miles. Fluid ageing becomes a primary factor: thermal and oxidative stability is vital for preventing lubricant breakdown over longer periods and ensuring that electrical, compatibility and wear performance is maintained right up to the oil change.
Testing times
These new needs mean it is no longer enough for ETF to pass existing industry tests. Balancing all-round performance with reliability and longevity means working closely with OEMs at the earliest stage of development, devising suitable lubricant tests, based on prototype hardware, to better predict real world performance.
