STRUCTURAL CERAMICS OFFER exceptional properties in terms of low density and endurance at very high temperatures, those exceeding 1000°C. These and other unique properties such as low thermal conductivity can be harnessed to serve the material needs of the future engines. In the interest of fuel efficiency and multi-fuel capability, future engines will operate at higher temperatures and be lighter in weight. Towards this end, partially stabilized zirconia (PSZ) and SiAlON components were engine tested. In a diesel engine, PSZ exhaust valves seating on PSZ seat inserts failed prematurely due to thermal shock. PSZ seat inserts showed no damage. SiAlON exhaust valves seating on metal seat inserts endured 1000 hours of cyclic operation with the exception of one lock groove failure.