Using dichromatic interferometry,the transition of lubrication regimes was experimentally observed in balldisc contact with a high viscosity gear oil,and the lubrication regime transitions were quantitatively analyzed under different speeds and loads.The results show that,under fully flooded conditions,transition from elastohydrodynamic lubrication (EHL) to hydrodynamic lubrication (HL) is obtained with increasing speed,and there is an obvious transition interval between the two kinds of lubrication states.However,an opposite transition fashion i.e.from HL to EHL can be found by increasing loads.In the experiments with a fixed amount of lubricant,the transition between fully flooded and starved regimes are also observed.