While you can create your own peanut butter with little more than a roasting pan and a blender, making actual cooking oil from peanuts requires an oil press. Presses designed for home use allow you to feed seeds and nuts into the top, and, by cranking the handle, collect peanut oil underneath it. An attached oil lamp, or press cage, gently warms and softens the nuts, making them easier to process. Use the crushed nut meats in baked goods, as a compost material, or to feed backyard livestock.
Shell the peanuts. For every 4.5 pounds of peanuts you process, you can expect about 1 quart of peanut oil.
Attach the oil press to your work surface with the clamp included with it. Preheat the press cage attached to the oil press, according to the manufacturer's instructions. This normally involves setting up a wick and kerosene oil, and setting the gauge for the lamp to begin burning. Let the press cage heat for 10 minutes.
Place a funnel into the feed inlet and a sturdy jar to catch the oil just under the oil outlet. It's also helpful to set a paper plate under the spout that expels the nut solids.
Fill the funnel about halfway with peanuts. Begin turning the crank of the oil press.
Continue adding peanuts to the feed inlet as you turn the crank of the press. Check the jar to ensure that oil is coming out of the oil press as you turn the crank.
Leave the oil to stand in the jar for 24 hours. Once the particles have settled to the bottom, strain the oil through a sieve into a clean bottle or jar, leaving the sediment-like material behind.
Seal the bottle or jar tightly, and store it away from heat and light.
Some oil press manufacturers may specify that shelling is not needed to process peanuts into peanut oil. Taking the time to shell the peanuts, however, makes the cranking go easier, and also enables you to use the nut-cake byproduct in cooking.
Keep peanut oil in a dark cupboard rather than in the refrigerator.
Making the oil in small batches may be prudent while you are new to oil making. Commercial peanut oils can last about 6 months at room temperature, but the potential for bacteria getting into home-processed foods is higher. Discard any oil that looks, smells or tastes off to you.