Red Line® Lead Substitute is a safe and effective valve seat protection additive which is designed for use in engines which require the protection of lead. Tetraethyl lead was originally designed as an octane enhancer, but it was soon discovered that the metallic oxides which result from combustion form a protective coating on valves which prevent micro welding of the valve seat to the valve face under high temperature operation. This welding of the two hot pieces of metal causes the removal of the softer seat metal and subsequent recession of the valve into the cylinder head. Wear debris then contributes to valve stem and valve guide wear. Valve recession causes poor sealing of the compression gases, which means loss of power and fuel economy, poor idle and drivability, and the eventual need for cylinder head replacement.