An oil filter is a device that used to decontaminate oil that contains suspended impurities. The important application is in forming part of the lubrication system of engines in which filters are typically detachable units due to the need for regular service or replacement. The filtration of oil in engines is essential for enhancing longevity and performance.

Oil fired water heaters use an oil burner and a combustion chamber (similar to an oil-fired furnace), which is located below the tank, as the heat source to heat the water. When the thermostat (at the bottom of the tank) senses that the water temperature has fallen below the preset limit, the oil burner will ignite. A jet-like flame is created in the combustion chamber to heat the bottom of the tank. In addition, the hot exhaust gases from the combustion chamber are vented either through a hollow core at the center of the tank (like a gas-fired system) or around the tank to help heat the water. The exhaust is then passed into the vent connector and directed to a chimney flue.

An oil free compressor uses special structure to interface the engine and compressor. In an oil-free compressor, the air is compressed entirely through the action of the screws, without the assistance of an oil seal. These are used in applications where entrained oil carry-over is not acceptable, such as medicial research and semiconductor manufacturing.