Claims 57% fuel efficiency: http://www.liquidpiston.com/technologycycle/tid/1.html
"The LiquidPiston engine is based on a patent-pending thermodynamic cycle, called the "High-Efficiency Hybrid Cycle" (HEHC), which borrows elements from Otto, Diesel, Atkinson, and Rankine cycles. Several critical design features make the LiquidPiston engine architecture both versatile and capable of outperforming conventional engines on all parameters. LPI’s engine is architected to have the following unique properties: High fuel efficiency of 57% at peak, and 50% at part-load High power density of 1 Hp / Lb Simple design with low part count Multi-fuel capable: diesel, JP8, gasoline, natural gas, bio-fuels Low noise: the engine has low pressure exhaust and no poppet valves" <more>
