Heat the corn oil in a large pot over medium heat. Stir in the corn kernels once hot. When the first couple of kernels pop, stir in the white and brown sugars. Cover the pot with a lid, and agitate the pot in a circular motion on the stove. Allow the corn to pop, agitating constantly, until the rate has slowed down to one pop every two or three seconds. Remove the pot from the stove, and shake the pot until the popping stops. Pour into a large bowl, and allow to cool to room temperature. Break apart the large clumps of popcorn by hand, and season with salt to taste.