Engine Tuning
E85 & Ethanol Blend Calculator
Calculate exact gallons of E85 and pump 93 required to hit custom ethanol blend targets (E30, E50, E85).
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How to Use This Tool
- Enter total tank capacity in gallons.
- Set current tank ethanol content (E10 from pump gas, or existing blend).
- Choose your target blend (E30, E50, E85, etc.).
- Add the calculated pump gas and E85 volumes to reach the target.
The Formula & Physics Behind the Math
Volume balance: (gallons E85 × E85% + gallons pump × pump%) ÷ total gallons = target %. Solving for E85 gallons: E85 = tank × (target − pump%) ÷ (E85% − pump%). Remaining volume is pump gas. Real-world blends vary with fuel station labeling and seasonal E85 content.
Frequently Asked Questions
Do I need a flex-fuel tune for E30?
Most forced-induction setups require a dedicated tune for ethanol blends above E10. Consult your tuner — never guess on boost and timing.
Is E85 always 85% ethanol?
Winter blends can be E51–E83 depending on region. Adjust the E85 station rating field if your station posts actual content.
Can I mix directly in the tank?
Yes — add pump gas first if the calculator calls for it, then E85, and drive briefly to mix. For precision, blend in a fuel jug before pouring.