That answer is very simple: By re-burning exhaust gases, you are not burning "new" fuel, there by consuming less fuel from the tank at one time. A lot of vehicles have this feature. One is the Ford Ranger with the four-cylinder and the new Dodge Hemi V-8. Both have intake plugs and exhaust plugs. By burning less "new" fuel, you save money and go farther on that one tank of gas.
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