How do you fill an oil heater?

To fill an oil heater, first ensure the unit is turned off and unplugged for safety. Locate the filling port, typically found on the top or side of the heater, and remove the cap. Using a funnel, carefully pour in the appropriate type of oil, usually mineral oil, until it reaches the recommended fill level indicated on the heater. Finally, replace the cap securely before plugging in and turning on the heater.