The use of methanol as a “clean fuel” appears to be a viable approach to reduce air pollution. However, concern has been expressed about potentially high formaldehyde emissions from stoichiometrically operated light-duty vehicles. This paper presents results from an emission test program conducted for the California Air Resources Board (CARB) and the South Coast Air Quality Management District (SCAQMD) to identify and evaluate advanced catalyst technology to reduce formaldehyde emissions without compromising regulated emission control.An earlier paper presented the results of evaluating eighteen different catalyst systems on a hybrid methanol-fueled test vehicle. (1)* This paper discusses the optimization of three of these catalyst systems on four current technology methanol-fueled vehicles. Emission measurements were conducted for formaldehyde, nonmethane organic gases (NMOG), methanol, carbon monoxide, and oxides of nitrogen emissions. The vehicles were operated on a chassis dynamometer using the Federal Test Procedure (FTP), Highway Fuel Economy Test (HFET), and New York City Cycle (NYCC). The three catalyst systems evaluated included, electrically-heated plus original equipment manufacturer (OEM), manifold plus close-coupled, and close-coupled alone. One catalyst system was selected for future short and long term durability testing on each vehicle. Selections were made to achieve a variety of emission control systems that were effective in formaldehyde and regulated emission control. All systems selected for durability evaluations gave average formaldehyde emission levels of less than 15 mg/mi.