20 000' in ISA 2500 RPM and 31" = 65% power @ 200kt. Supposed to use 139 LpH. Ours used 195 LpH. We thought fuel was stolen. Proved not to be the case. Checked the fuel control unit, the MP gauge, the Tacho. They could not fault anything, yet the fuel consumption was too high. We leaned to 50 degrees rich of peak.