Adjust oven rack to center position and preheat oven to 425 degrees F. Scrub potatoes clean under cold running water and rub with oil. Wrap potatoes individually in foil and place on a rimmed baking sheet. Bake until a skewer inserted into the potatoes through the foil meets some resistance about a half-inch under the surface, about 30 minutes. Remove from oven, carefully open foil, and place potatoes back on baking sheet on top of foil. Continue baking until a skewer inserted into the potato meets no resistance and the skin is crisp, about 30 minutes longer. Remove from oven and let cool 3 minutes.
