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Recent automotive engines are being produced with various types of fuel injection systems. One variation is the natural gas engine (LPG, CNG, etc. ) in which lubricating conditions become more severe than in conventional engines. Valve seats in such severe conditions require wear resistance. At the same time, automotive components are strictly regulated to exclude hazardous elements such as lead, a well known self lubricating element. New lead free materials have been developed for both inlet and exhaust valve seats. Some show better durability than lead infiltrated materials. For the purpose of heat and wear resistance, a tough matrix can be obtained from several types of homogeneously distributed alloy particles. Calcium fluoride ( CaF2 ) has also been found to provide a positive effect on wear resistance and self-lubrication.