MMT is a manganese containing metallic additive that is blended into some gasoline to increase the octane number.

Gasoline blended with MMT offers no performance advantage beyond gasoline of the same octane number without MMT. Gasoline blended with MMT has been shown to reduce spark plug life and reduce emission system performance in some vehicles. The manufacturer recommends using gasoline without MMT. Since the MMT content of gasoline may not be indicated on the pump, you should ask your gasoline retailer whether or not their gasoline contains MMT.

It is even more important to look for gasoline without MMT in Canada, because MMT can be used at levels higher than those allowed in the United States.

MMT is prohibited in Federal and California reformulated gasoline.