How to tell when cooking oil is hot
When you first add oil to a pan, it will be relatively stagnant, and should coat the pan as you move it around. As it heats up, the oil will start to move from the center of the pan and split into streams across the pan’s surface. If you tilt the skillet, the oil will shimmer like ripples in a lake, letting you know it’s time to add the food. But if you notice smoke — a few wisps are okay — it is too hot and you should turn down the heat.