Are the Reductions in Vehicle Carbon Monoxide Exhaust Emissions Proportional to the Fuel Oxygen Content?

Exhaust emissions results from two vehicle test programs demonstrate that CO reductions created by using oxygenated fuels are very vehicle specific and are usually not proportional to the amount of oxygen in the fuel. In vehicles with oxidation and three-way catalyst systems, a MTBE blend with 2.0 weight percent oxygen was, on average, 80% as effective at reducing the CO emissions as a 3.5 weight percent oxygen ethanol blend. The noncatalyst vehicles, on average, showed CO reductions proportional to fuel oxygen content. The vehicles with three-way catalysts and adaptive learning systems showed very little response to the oxygenated fuels.