The scoring-load capacities of the vegetable oils were studied by using a power-circulating gear test rig. The tests were carried out under a slash-pan lubrication. From the tests, the following results were obtained. (1) The scoring-load capacities increased in following order : Turbine oil < Soybean oil < Corn oil < Rapeseed oil. The normal load per unit face width at the incipient stage of scoring when lubricated with the rapeseed oil was approximately 1.7 times as large as that when lubricated with a turbine oil. (2) The critical temperature at a risk for scoring with the rapeseed oil was about 400℃, and was the highest of all test oils. (3) The acceleration of the gear box when scoring occurred increased significantly, and consequently surface failure by scoring could be detected by means of the measurement of acceleration due to vibration of the tested gear box.