Single vs. Dual

• A dual exhaust system will increase the gas mileage of your vehicle. Above and beyond increasing your gas mileage, an added bonus to choosing a dual exhaust system is an increase in horsepower.
  
  

Types

• There are two types of dual exhaust systems: true dual exhaust and dual exiting exhaust. Dual exiting exhaust systems have one catalytic converter, one muffler and a split tailpipe. True dual exhaust systems have two catalytic converters, two mufflers and and two tailpipes.
  
  

Exhaust Systems and Engines

• Cars with four-cylinder engines cannot have a true dual exhaust system installed because they have only one exhaust manifold. Vehicles with six- or eight-cylinder engines have exhaust manifolds on both sides of the engine and therefore can accommodate a true dual exhaust system.
  
  

Tailpipes

• Contrary to popular belief, having one or two tailpipes makes no difference in your engine's performance. This is merely a cosmetic choice.