Oil on hot pans

"In their tests, the oil heated up faster in the centre of the pan. Surface tension tends to decrease in liquids as temperatures rise, which led to a gradient in surface tension across the pan. The stronger tension toward the edges pulled the less cohesive oil at the centre outwards and deformed the surface of the layer."

So you end up with a dry spot in the middle of your pan. And the food sticks. To defeat it, use some well-known techniques: "Increasing the thickness of oil will help to stop it reaching a critically thin level, while using a pan with a more massive bottom will spread heat more evenly and prevent temperature gradients. Using moderate heat will also help, as will stirring the food regularly, recipe permitting."