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If you run your car on E85, you’ve likely heard the horror stories of the dreaded "Black Goo." You go to start your car after it’s been sitting for a few weeks, and it misfires, idles poorly, or won't start at all. Upon pulling the injectors, you find a sticky, tar-like substance coating the tips.
This isn't just a myth; it is a documented chemical reality of using ethanol fuels. But what actually is it, and how can you stop it from ruining your expensive high-flow injectors?
What is the "Black Goo"?
Contrary to popular belief, "Black Goo" isn't actually the ethanol itself breaking down. Chemical analysis typically shows that this residue is a combination of:
- Heavy Hydrocarbons: These are residual oils and heavy elements left over from the petroleum refining process (the 15% of "gasoline" in E85).
- Additives: Certain detergents or additives used in cheap pump fuels.
- Polymerization: When these specific hydrocarbons are exposed to ethanol and heat, they can form a sticky, varnish-like polymer.
Why Does It Clog Injectors?
The "Goo" tends to form right at the injector tip (the pintle or orifice plate). This is the hottest part of the fuel system because it sits directly inside the intake runner or cylinder head.
When you turn your engine off, the remaining fuel in the injector tip evaporates due to engine "heat soak." The ethanol evaporates quickly, leaving behind a concentrated residue of those heavy hydrocarbons. Over time, this builds up into a crust or a sticky film that disrupts the spray pattern or physically glues the injector shut.
How to Prevent the Build-Up
The good news is that Black Goo is preventable. You don't have to give up the power gains of E85; you just need a better maintenance routine.
1. Use High-Quality Fuel
Not all E85 is created equal. Cheap pump E85 often contains more contaminants than dedicated "race" ethanol (like Ignite or VP Racing). If you must use pump E85, try to stick to high-turnover stations where the fuel is fresh.
2. The "Pickle" Method (Flush with Petrol)
If you plan on leaving your car in the garage for more than two weeks, don't leave it "wet" with E85.
- The Process: Run your tank low, fill it with standard 98-octane gasoline, and drive the car for 15–20 minutes.
- The Result: This flushes the ethanol out of the lines and injectors, "pickling" the system in stable gasoline that won't evaporate and leave residue.
3. Use an Ethanol-Specific Fuel Additive
There are several specialized fuel treatments designed specifically to keep these deposits in suspension so they pass through the injector rather than sticking to the tip.
4. Stainless Steel Internals
Ensure you are using injectors designed for E85. At Excess Injectors, our performance injectors feature stainless steel internals. While this doesn't stop the goo from forming on the outside of the tip, it prevents internal corrosion of the injectors, another common E85 issue, from compounding the problem.
How to Clean "Gooey" Injectors
If you’ve already caught the "Goo," don't panic. In most cases, the injectors aren't broken; they are just restricted.
- Professional Ultrasonic Cleaning: This is the only way to truly restore an injector. The ultrasonic waves break down the polymers that chemicals alone can't touch.
Avoid "Poke" Cleaning: Never try to clean the tips with a needle or wire brush. You will damage the precision-machined orifice and ruin the spray pattern.