Wikipedia: Methylcclopentadienyl manganese tricarbonyl (MMT)
Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organometallic compound with the formula (CH3C5H4)Mn(CO)3. Marketed initially in 1958 as a supplement to the gasoline additive, tetraethyl lead to increase the fuels octane rating, MMT was later used in unleaded gasoline.[1] Although banned as a gasoline additive in the United States from 1977 to 1995, MMT has been used in Canadian gasoline since 1976 and was recently introduced in Australia. It is sold under the tradenames HiTec 3000 and AK-33X.[2]