Gearbox oil heaters activate when ambient temperature falls below which value?

• A. 12°C
• B. 0°C
• C. -5°C
• D. 8°C

Answer: (C)

Gearbox oil heaters are set to kick in when ambient conditions cause the oil to become too viscous to lubricate effectively. The activation point is around minus five degrees Celsius because, below that temperature, oil thickens enough to make starting and gear operation harder, increasing wear and reducing lubrication efficiency. The heater warms the oil to bring its viscosity to a more workable level, protecting gears and seals and helping the gearbox reach normal operating conditions sooner. At temperatures warmer than that threshold, the oil remains fluid enough, so heating isn’t needed and the heater stays off.