Why does an engine with an aluminum block require additional Microlon?

The Microlon resin fills in the pore structure of the metal inside of the engine. Since aluminum has a much more open pore structure, more of the Microlon resin is required to fill in the surface of the metal and form the Microlon film. The key to the Microlon effect is forming the film and it simply takes more product to fill in the pore structure of the metal in an aluminum block.