How much more fuel does E85 need compared to pump gas?
Roughly 25–45% more, depending on how you measure it — sources differ.
- Stoichiometric ratio: E85 is about 9.7–9.8:1 vs about 14.7:1 for gasoline (LSX Magazine), so it takes much more fuel mass for the same air.
- Fuel-system sizing: Performance Racing Industry says plan for 30–40% more flow capacity.
- Power math: LSX Magazine, using brake-specific fuel consumption (0.80 vs 0.55 lb/hp-hr), works out to about 45% more fuel mass for the same power.
- Real-world use: eFlexFuel reports about 25–30% more fuel consumed on straight E85 (E50 only 5–10%).
Sources differ: the percentages above measure different things (flow capacity, power-equivalent mass, and observed consumption), and pump "E85" varies — as little as 51% ethanol. For sizing, use the higher figures so the fuel system has headroom.
See fuel, E85 & boost.
Confidence: medium — sources disagree or are limited; check the sources below.
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Sources
- Fuel For Thought: Sizing Port Fuel Injectors for High-Performance Engines — LSX Magazine
- eFlexFuel eFlexPlus Manual — eFlexFuel
- PRI Education: Converting From Pump Gas to E85 — Performance Racing Industry