Oil refinery equipment. Gas compressor at an oil refinery. Gas compressors are usually used to compress a gas for transport. Compressing a gas also raises its temperature, unless it is cooled and liquified. Petroleum gases (mostly butane and propane) can be obtained from crude oil and liquified to form LPG (liquified petroleum gas), which is used as a fuel. Natural gas (mostly methane) can also be compressed and used this way. Photographed at ExxonMobil's Fawley Oil Refinery and Chemical Plant, Hampshire, UK.