E85 flex fuel myths, rumors, and other misconceptions
Common Myths About E85: Debunking the Misinformation
E85 ethanol-based fuel has gained significant popularity in the performance and motorsports world due to its high octane rating, cooling properties, and cost-effectiveness compared to race gas. However, despite its widespread use, there are many myths and misconceptions surrounding E85 that cause hesitation among enthusiasts. In this article, we’ll break down some of the most common myths about E85 and provide technical explanations to set the record straight.
Myth #1: “E85 Will Ruin Your Fuel System”
Reality: Not If You Use Compatible Components
One of the most widespread misconceptions about E85 is that it will destroy fuel system components due to its ethanol content. While it’s true that ethanol is more corrosive than gasoline, modern fuel systems—especially those designed for flex-fuel vehicles—are built to handle ethanol without issues.
Why This Myth Exists
Older cars (especially those built before the mid-2000s) often used rubber fuel lines, seals, and gaskets that were not designed to withstand high ethanol content. Over time, ethanol can degrade certain materials, leading to leaks and potential failure.
The Truth
To run E85 safely, you need:
Ethanol-compatible fuel lines – Use PTFE (Teflon-lined) or ethanol-rated rubber lines to prevent degradation.
Upgraded fuel pump and injectors – Since E85 requires ~30% more fuel flow, ensure your pump and injectors can handle the extra demand.
Stainless steel or anodized aluminum fittings – These resist ethanol corrosion better than standard metals.
Modern vehicles and aftermarket fuel system components are specifically designed to handle ethanol, making this myth outdated for most performance builds.
Myth #2: “E85 Doesn’t Work in Cold Weather”
Reality: Cold Starts Can Be Tricky, But There Are Solutions
Another common concern is that E85 makes cold starts difficult, especially in colder climates. This stems from ethanol’s lower energy density and higher latent heat of vaporization, which makes it harder to ignite in freezing temperatures.
Why This Myth Exists
• Ethanol absorbs moisture, which can cause phase separation in extreme cold.
• The higher ethanol content makes vaporization more difficult, leading to longer crank times.
• Factory flex-fuel vehicles typically run a winter blend with lower ethanol content (~70% instead of 85%) to improve cold-start performance.
The Truth
Cold starts on pure E85 can be more challenging, but the problem is manageable:
Use a proper standalone ECU – Many ECUs allow for cold start enrichment and cranking fuel adjustments.
Add a flex-fuel sensor – This automatically adjusts fueling based on ethanol content.
Use a winter blend – Many fuel stations offer E70 in colder months to improve cold-weather performance.
Tuning for cold starts properly makes E85 just as viable in cold weather as gasoline.
Myth #3: “E85 Isn’t Worth It Unless You’re Turbocharged”
Reality: E85 Benefits NA, Supercharged, and Turbo Engines
While it’s true that turbocharged engines often see the biggest gains from E85, naturally aspirated and supercharged engines can also benefit significantly.
Why This Myth Exists
• Turbocharged engines make more power due to increased boost levels, so people assume E85 is only useful for forced induction.
• Some think that E85’s cooling effect is only beneficial when dealing with high intake air temperatures.
The Truth
E85 benefits any high-performance engine by providing:
Higher effective octane (~105-110) – Allows for more ignition timing advance and higher compression ratios.
Cooler combustion temperatures – Reduces the likelihood of detonation.
More consistent power delivery – Less knock retard means a smoother powerband.
NA engines, especially high-compression setups (e.g., 12:1+), see improved efficiency and power on E85. Supercharged applications also benefit from reduced heat soak and detonation resistance.
Myth #4: “E85 Requires Constant Tuning and Maintenance”
Reality: A Proper Flex-Fuel Setup Makes It Simple
A common concern is that running E85 means constantly adjusting fuel maps and maintaining the system.
Why This Myth Exists
• Ethanol content in pump E85 varies (sometimes it’s closer to E70 or E80).
• Some drivers experience inconsistent performance if they don’t account for ethanol content changes.
• Older tuning methods required swapping maps manually when switching fuels.
The Truth
A modern flex-fuel system with the right ECU makes everything automated:
Flex-fuel sensors automatically adjust the tune based on ethanol percentage.
Standalone ECUs like Haltech, Motec, AEM, and FuelTech allow real-time tuning adjustments.
Quality ethanol-rated filters prevent fuel system issues from debris or moisture absorption.
Once properly set up, E85 requires no more maintenance than regular gasoline.
Myth #5: “E85 Burns Too Fast and Reduces Fuel Economy”
Reality: Yes, E85 Burns Faster, But That’s Not the Whole Story
It’s well known that E85 has lower energy density than gasoline, meaning you need more fuel to produce the same power. However, this doesn’t necessarily mean it’s inefficient for performance use.
Why This Myth Exists
• Gasoline contains about 34 MJ/kg of energy, while ethanol contains 26.8 MJ/kg, meaning you need more ethanol for the same energy output.
• Many people notice a drop in miles per gallon (MPG) when switching to E85, which they assume means wasted fuel.
The Truth
E85 allows for more aggressive tuning, meaning power gains compensate for increased fuel use.
E85’s cooling effect increases efficiency, leading to better combustion and sometimes offsetting some of the MPG loss.
Cost per horsepower is often cheaper than race gas, making E85 a cost-effective performance fuel.
For daily drivers, E85 may not be ideal due to range limitations, but for performance applications, the benefits far outweigh the downsides.
Conclusion: E85 Is a High-Performance Fuel with Manageable Tradeoffs
E85 is often misunderstood due to outdated information and misconceptions. While it does require proper fueling components, tuning, and cold-start considerations, modern technology makes it a highly effective and affordable alternative to race gas.
If you’re looking to increase power, improve knock resistance, and take advantage of a high-octane fuel, E85 is worth considering—regardless of whether you’re running a turbo, supercharger, or high-compression NA setup.
Final Takeaways:
E85 won’t ruin your fuel system if you use compatible components
Cold starts can be tuned properly for ethanol blends
NA and supercharged engines can benefit just as much as turbo cars
Flex-fuel tuning eliminates the need for constant adjustments
Fuel economy drops, but power gains and cost-effectiveness compensate
Lets get you setup with a flex fuel setup on your race car, or truck!