Why do tuners use E30 or E50 instead of full E85?

Many fuel systems (injectors and pumps) cannot support the high volume required for full E85. A partial blend like E30 gives a significant octane boost without overloading the fuel system.

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Fuel & Efficiency

Ethanol Blend

Q: What is an ethanol blend?

An ethanol blend is a mix of standard gasoline and ethanol. For example, E30 means the fuel contains 30% ethanol and 70% gasoline.

Q: How do you mix E85 safely?

To mix E85 safely, use an ethanol blend calculator to find the exact volume of E85 and pump gas to add to your tank. Always test your pump E85 content first, as it varies by season.

Mix two fuels to hit a target ethanol percentage.

Blend Estimator

Final % Ethanol = ((A × V_A) + (B × V_B)) / (V_A + V_B)

Fuel A (e.g. Pump Gas)

Ethanol %:

Volume (Gallons or Liters):

Fuel B (e.g. E85)

Ethanol %:

Volume (Gallons or Liters):

Scratchpad

Session-only notes while you work.

Expand to jot temporary notes. Nothing is saved after you leave.

Comparison Log & Run History

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Perform a calculation and click "Log Current Run" to save it for side-by-side comparison.

Runs are stored temporarily in your active session and clear when you leave this page.

Quick-Swap Unit Converter

Convert common automotive units without leaving this tool.

Expand for volume, torque, pressure, weight, length, speed, and temperature conversions.

About this tool

The BuildLockr ethanol blend calculator helps you mix fuel accurately for your tuned engine. Use this tool to calculate exactly how much E85 and pump gas you need to reach your target blend. Whether you are aiming for an E30 mix or E50 mix, this E85 mixing tool handles the math. This helps drivers avoid dangerous lean conditions by ensuring their fuel mixture matches their engine tune.

Quick Preset Blends

These presets mix generic E10 pump premium gas with standard E85.

What is an Ethanol Blend?

An ethanol blend is a mixture of standard gasoline and ethanol. For example, an E30 blend means the total fuel composition is 30% ethanol and 70% gasoline.

How do you mix E85 safely?

To mix E85 safely, determine the current ethanol content of the E85 from the pump (it ranges from 51% to 85%), input your pump gas content (usually 10%), and use our calculator to find the exact volumes to add.

Why do tuners use E30 instead of full E85?

Many stock fuel pumps and injectors max out on full E85. Mixing to E30 provides a significant octane boost while keeping fuel volume requirements within the limits of the factory fuel system.