What kind of oil is used in a hydraulic coupling?
2 Answers
Hydraulic couplings use different oils depending on their type: For refilling: Typically, flame-resistant hydraulic oils such as No. 8 hydraulic oil, No. 32 hydraulic oil, No. 20 turbine oil, or No. 6 and No. 8 hydraulic transmission oils can be used. It is important to note that gear oil should not be used, and hydraulic couplings strictly prohibit oil injection. A hydraulic coupling, also known as a fluid coupling, is a mechanical device used to connect a power source (usually an engine or motor) to a working machine to transmit rotational power. A hydraulic coupling, also known as a fluid coupling, is a mechanical device used to connect a power source (usually an engine or motor) to a working machine to transmit rotational power.
I've been working in automotive repair for nearly twenty years, and for torque converters, automatic transmission fluid like the common Dexron or Mercon series works best. This type of oil has moderate viscosity, doesn't thin out under high temperatures and speeds, and ensures stable power transmission while lubricating internal components. Using the wrong oil, such as regular engine oil or gear oil, can cause the torque converter to overheat and wear out, leading to power loss, slippage, and in severe cases, requiring a full replacement. For routine maintenance, check the fluid level—just open the torque converter housing to inspect. If the fluid appears black or has contaminants, it's time for a change. Always choose the specification listed in the vehicle's manual, as requirements vary by model. Using cheap, incorrect oil can end up costing more in repairs. Regular maintenance is key—typically, change the fluid every few tens of thousands of kilometers to extend the torque converter's lifespan by over a decade.
