Generally speaking, the older/ more oxidized/ more roasted degree the oolong is, the higher the water temperature should be. That is to say, if your oolong is aged, oxidized or roasted, you’d better brewing it with a higher temperature.
The proper water temperature for brewing oolong tea is between 85–95 degrees Celsius or 185–205 degrees Fahrenheit. You may control the temperature with a thermometer. There is also another way to measure the temperature, namely cooling the just-boiled water in another vessel to the ideal temperature with your oolong tea.
These are quite important for brewing delicate oolong tea. Quality teas can be steeped 4-6 times.
Related: Oolong Tea Preparation