The answer to this question is yes; an aftermarket performance exhaust can improve your fuel economy. It does not just enhance the power of the car. This is because the performance exhaust will enhance the overall airflow of the exhaust gases, which will help the engine work more efficiently. The best aftermarket performance exhaust can improve your fuel economy by 5%! However, if you buy a cheap aftermarket exhaust made of low-quality materials, you will end up hurting your fuel consumption. That is why it is better to do your research and pick the right one for your truck.