Once established in the cruise, the pilot noticed that the right auxiliary fuel gauge indicated an above average consumption. When the fuel selector was changed to right main tank, the excessive consumption remained. The pilot decide to continue to destination after calculating his endurance at the indicated fuel consumption. At this stage the aircraft had passed the equal time point. He cross-fed fuel from the left wing fuel tanks and kept both engines running. The aircraft arrived with 120 litres of fuel on board. A post flight inspection by maintenance staff found that the right wing was stained underneath with avgas. Further investigation found that the fuel delivery hose to the fuel control unit was undertorqued. Removal of the fuel finger filter found that the adapter o-ring was damaged.