In a sauce pan, add oil and heat til hot, but not smoking. Add onion, and cook 2-3 minutes. Stir in saurerkraut, and let simmer about 5 minutes. Add ketchup and Mustard. Simmer about 3 more minutes til flavors mingle well. In another pot add hot dogs and enough water to cover. Bring to a boil. I like mine splitting open so I boil them longer. Drain. Add hot dogs to buns, and top with sauerkraut mixture. Wrap hot dogs individually in aluminum foil, and place on a cookie sheet in a preheated 200 degree oven. For about 30 minutes while you are preparing the rest of dinner. Take them out and enjoy. Tastes like the dogs from the ball park.