A new concept of a semicryogenic tank for storage and supply of natural gas into the cylinders of an internal combustion engine is presented. It allows the gas to be pressurized before injection and uses the heat entering the tank as the means to evaporate the natural gas introduced in a liquid phase to the tank. To limit the heat transfer to the tank and the gas pressure increase, the semicryogenic tank has to be well insulated. However, it has to be also preheated to accelerate the gas pressure increase, as required. To maintain the right pressure and temperature of natural gas an electronic control of the semicryogenic tank is needed. The gas preheating system uses the waste heat of engine exhaust gases and, therefore, contributes to the increase of the thermal efficiency of the engine through the injection of hot natural gas. Practical informations are also given for manufacturing of the semicryogenic tank based on the use of regular standardized cylinders for compressed natural gas.