Oil column heaters, or simply referred to as oil heaters, are one of the forms of home or workplace heating. They operate by heating up a reservoir of oil which then circulates around the fins of the heater. They are 100% efficient.
They can be purchased for as little as NZ$39 (2019 prices). Some are of poor quality with the castors or the castor holding bracket failing within a short period.
A mineral oil with various additives is used to transfer the heat from the element to the radiating fins.