In a large skillet, heat the oil over medium-high heat. Add the ground beef and cook, stirring frequently, until the meat is browned on all sides, 5 to 7 minutes. Stir in the ketchup, Worcestershire sauce, and mustard. Cook and stir for 1 minute. Remove the skillet from the heat and add the onion and celery. Saut? until softened, 2 to 3 minutes, then stir in 2 tablespoons of the mayonnaise. Season with salt and pepper to taste. Place the patties on the buns and fry until golden brown, 3 to 4 minutes on each side. Serve warm.