Manganese is a silvery-gray metal resembling iron. It is hard and very brittle, difficult to fuse, but easy to oxidize. Manganese has no satisfactory substitute in its major applications, which are related to metallurgical alloy use. Manganese is essential to iron and steel production by virtue of its sulfur-fixing, deoxidizing, and alloying properties. The second large application for manganese is as alloying agent for aluminium.Methylcyclopentadienyl manganese tricarbonyl is used as an additive in unleaded gasoline to boost octane rating and reduce engine knocking.