Today's emissions of harmful pollutants from new cars are a dramatic reduction compared to cars made in the 1960s. This not only improves the air we breathe compared to 25 years ago, but has led to a dramatic increase in fuel economy.
The centerpiece of this successful pollution reduction program was the result of the catalytic converter. Today's automobiles are meeting emission standards that require reductions of up to 97 percent for Hydrocarbons (HC), 96 percent for Carbon Monoxide (CO), and 90 percent for Oxides of Nitrogen (NOx) compared to the pre-control levels emitted. This has offset a more than doubling of the number of vehicle miles traveled (VMT) in the U.S. over that time.
Typically, as few as 10 percent of the vehicles in use contribute to as much as 50 percent of the pollution problem, typically because they are very poorly maintained. The American driving public can help make a real contribution to clean air by properly maintaining and using their vehicles. Some provinces now require all vehicles undergo a periodic emission inspection to ensure that your car's emission control system is functioning properly. The U.S. EPA estimates that the type of maintenance needed to correct excess pollution problems can improve fuel efficiency by up to 15 percent.
You should never tamper with your emission control systems. Not only is it against the law, but with today's sophisticated automobile technology, emission controls have been optimized to maximize fuel economy and performance. Tampering will not only increase harmful pollution, but reduces your car's fuel economy and performance.