For better automotive fuel economy and environmental quality in an engine, a mixture heating chamber (1) is attached to an engine exhaust manifold. A U-shaped air tube (7) is connected to the mixture heating chamber (1) for supplying heated air to the chamber (1). A vapor supply fuel line supplies the chamber (1) with liquid fuel, the liquid fuel being sprayed from the vapor supply fuel line (19) into a portion of the U-shaped air tube (7) located inside the chamber (1) resulting in vaporization of the liquid fuel. The mixture heating chamber (1) is partially filled with copper pads (3) for fire retarding purposes and its interior is lined with a felt-liner (5) which retains the liquid fuel present and also acts as a wick. A fuel selector switch (21) allows fuel to be channelled through a vapor supply fuel line (19) and into the mixture heating chamber (1) or into a main fuel line (39) which connects directly to the carburetor (41).