Running ethanol has become the standard for making horsepower in modern muscle cars. The transition from pump gas to corn is almost a requirement for any serious boosted LS build. But relying on gas station E85 is a gamble. You never truly know the blend ratio, which fluctuates based on the weather and location. Sunoco aims to eliminate that variable with their race-proven ethanol lineup, now headlined by the new Sunoco EPX.
We caught up with the team at the 2025 PRI Show to discuss the chemistry behind the new fuel. Because Sunoco distills its own ethanol in Pennsylvania, they can guarantee the blend is identical every time you crack a seal. This consistency is critical when you are tuning on the edge. Sunoco EPX was developed as an evolution of their popular E85-R, but it is formulated for significantly higher stress levels.
The key difference is oxygenation. Sunoco EPX carries a 34 percent oxygen content, which is a jump up from previous formulations. This alters the stoichiometric air-fuel ratio to 9.4:1. While you will not find a traditional octane number on the pail, the fuel is rated to handle over 30 psi of boost without breaking a sweat. It provides the massive latent heat of vaporization that cools your intake charge while delivering the combustion stability needed for record-setting passes.
For racers who have pushed standard E85-R to its limit, or for those tired of testing every tank of pump gas, this is the ultimate upgrade. It delivers the cooling and power of ethanol with the scientific precision of a lab-grade race fuel.
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