 In this liquid state, natural gas is more than 2 times as dense as highly compressed CNG.LNG fuel systems function on any vehicle capable of burning natural gas.Unlike CNG, which is stored at high pressure (typically 3000 or 3600 psi) and then regulated to a lower pressure that the engine can accept, LNG is stored at low pressure (50 to 150 psi) and simply vaporized by a heat exchanger before entering the fuel metering devices to the engine.