- Drop the manifold into a shallow container — a large backing pan usually works — and fill it with a mixture of 80 percent water and 20 percent dish detergent. Mix it well, and submerge the manifold in the mixture overnight. You can speed this process and deepen the stain removal by heating the water to about 150 degrees Fahrenheit; just high enough that the soap doesn’t foam and boil over.
- Remove the manifold and scrub it with a paintbrush and more soap. The detergent should have softened and lifted most of the oil out, so you may only need to give it a slight scrubbing. Rinse the manifold and dry it with compressed air.
- Repeat this process with specialized aluminum cleaner; some manufacturers may make specific product recommendations, but any aluminum wheel cleaner works. Allow the manifold to sit for as long as you can, then remove it, clean it with a paintbrush and dry it with compressed air.