5 to 6 days before frying, figure out how much oil you’ll need. Before you fill your pot with oil, do a test run with water. Fill a 30-quart pot halfway with water, measuring with a quart size measuring cup if possible. When the pot is half filled with water, place the frozen turkey (still in its packaging) into the water. Add more water if needed to cover the turkey. Note the number of quarts of water you used to fill the pot and cover the turkey by about 1 inch — that’s how much oil you’ll need on fry day (don’t use more than 4 1/2 gallons). After you remove the turkey from the water, you can also mark the outside of the pot with a permanent marker to note the fill line for frying.