The reason you choose to tune your car is to maximize performance. The higher the quality of the fuel, the better the performance will be. We NEVER recommend running regular fuel in a vehicle that is tuned. If you are the type that wants to know if you can run Ethanol (E85) or race gas (100-109), the answer is kinda. Some vehicles have the fuel components factory that will allow you to run E85. Other vehicles it can be corrosive and damaging. You can always run race gas as long as it is unleaded. Do not run leaded jet fuel as this will damage O2 sensors.