Ecofins Vortex Generator Fuel Saver *Manufacturer recommends 1 EcoFin per 4"/~100mm, or 3 EcoFins per 1'/~300mm. *Reduction of drag from EcoFins can save you as much as a 5% on fuel! *EcoFins are most effective when used on the sides and top of your cab/trailer. Vortex Generator Fuel Saver ... See More