I live in Virginia, and at times it gets high 90s into the low 100s. I topped off my radiator fluid, I didn't change it altogether, and I also added a half quart of oil, synthetic 5W-30. Since then it will climb into the mid to high 90s for temperature, but it hasn't hit 100. Does anyone know how often to change radiator fluid altogether? I put mine in about 9 months ago. Does anyone have a recommendation for a certain type of fluid?

I am going to look into that resistor thing also, my fans don't come on at all unless the AC is on.