A plug valve and stem sealing assembly capable of preventing leakage under demanding environmental and operating conditions while also improving the reliability of the valve seal. The valve includes a body, a flow-element, a bonnet and a self-adjusting stem sealing assembly. The body has a first port and a second port with a passage configured to flow a media extending between the first port and the second port. The flow-element is positioned between the first and second port and has a stem configured to actuate the flow-element between a closed position and an open position. The bonnet may be secured to the valve body and configured to secure the flow-element and stem sealing assembly in position. The self-adjusting stem sealing assembly is positioned adjacent to the stem and is configured to prevent media leakage from the valve.