Bearing lubrication for high speed application (above 20,000 rpm) has significant influence on the bearing heat generation and consenquently bearing operating temperature. For application in aerospace industry the selection of lubricant type, its amount and lubrication method should be carefuly conducted in order to achieve desired life and minimal weight. In this paper, experimental research was carried out in order to check whether and to what extent an open loop system can achieve similar bearing thermal behaviour as in a closed loop system. Tests were conducted on high-speed bearings of a turbo shaft engine. The experimental results showed that the open loop system, with oil mist lubrication, can achieve similar bearing operating temperature as the closed loop system, which operates with oil circulation, with the advantage of having a significantly lower mass. Also, a variation of lubrication conditions for open loop method, air pressure and oil amount, was carried out in order to minimize the operating temperature of high speed angular ball bearings. It has been shown that there is a combination of these two parameters that gives the least heating of high-speed bearings.