With burning you have to consider the fuels on the ground and the pine straw, etc, that is hanging on lower limbs. Humidity, wind, temperature, terrain all make a difference. I don't know what you are trying to save, but oaks are thin skinned and very susceptible to heat.
On privet you have to remember that they produce tons of seeds that will come up the next year. You don't have a good situation. Be very careful with chemicals.