While a chip might adjust the engine's parameters to deliver more power, this usually involves running the engine richer (more fuel) or at higher RPMs, both of which consume more fuel. Any perceived increase in mileage is usually negligible and often offset by the increased fuel consumption associated with the added power.
To improve fuel mileage in a Ford V10, focus on factors like proper maintenance (air filter, spark plugs, etc.), driving habits (avoiding aggressive acceleration and excessive idling), and potentially even aerodynamic modifications (though less impactful on a truck).
