Heat oil in large heavy pot over high heat. Working in batches add turkey parts and sauté until deep brown, about 15 minutes per batch. Return turkey parts to pot. Add vegetables and 18 cups of water. Bring to boil. Reduce heat to medium low. Simmer stock for 3 hours.
Strain into large bowl. If necessary, return stock to same pot and cook until reduced to four cups of stock (not including layer of fat). Cool stock slightly. Chill uncovered until cool, then cover and keep chilled up to four days. Remove and reserve fat layer on top before using.