NOVELTY - A catalyst composition, comprises: a reduction catalyst mixture including a first reduction catalyst and a second reduction catalyst; and an oxidation catalyst for increasing oxygen free radical formation during combustion; where the oxidation catalyst does not interfere with reduction reactions caused by the reduction catalyst mixture such that the reduction catalyst mixture is effective to reduce harmful emissions during combustion of the combustible fuel.    USE - As a catalyst composition useful in combustible fuel (comprising solid fuel and liquid fuel selected from diesel, gasoline, heating oil, jet fuel, bunker fuel, ethanol, and biodiesel) (claimed).    ADVANTAGE - The reduction catalyst mixture is effective to reduce harmful emissions during combustion of the combustible fuel. The reduction catalyst mixture and the oxidation catalyst are effective to increase the British thermal unit (BTU) output of the fuel, engine torque and engine horsepower; and improve fuel economy while reducing harmful emissions during combustion of a combustible fuel.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a composition comprising: a combustible fuel; reduction catalyst mixture including a first reduction catalyst and a second reduction catalyst; and an oxidation catalyst for increasing oxygen free radical formation during combustion; where the oxidation catalyst does not interfere with reduction reactions caused by the reduction catalyst mixture such that the reduction catalyst mixture is effective to reduce harmful emissions during combustion of the combustible fuel;    (2) preparing (M1) a composition for use as a fuel additive, involving: blending the first reduction catalyst and the second reduction catalyst in a carbon-based liquid fuel; where the mixture of the first and the second reduction catalysts is effective to reduce harmful emissions of the liquid fuel; and    (3) improving fuel economy while reducing harmful emissions during combustion of a combustible fuel, involving: providing a composition comprising a first reduction catalyst, a second reduction catalyst, and an oxidation catalyst; and mixing the composition with a combustible fuel; where the composition is effective to improve fuel economy while reducing harmful emissions during combustion of the combustible fuel.