Ethanol Blended Fuels

phase separation samples

Problems and Solutions


In 2006 the EPA Renewable Fuel Standard (RFS) mandated the use of ethanol blended fuels. Since that time, conventional gasoline has been blended with 10% ethanol (E10). This is known as the “blend wall” – the capped limit of ethanol content for gasoline. (Renewable Fuel Standard (United States), 2018) It is expected the EPA will increase the blend wall to 15% (E15) to meet the ever-increasing requirements created by the RFS. (IER, 2016) This is considered the maximum blend without major upgrades to petroleum industry infrastructure. Industry experts agree the majority of petroleum equipment is not manufactured to withstand ethanol above 15%.

Today over 90% of gasoline sold contains ethanol, producing unintended consequences and challenges to the industry. (Franklin Fueling Systems, 2012) The introduction of ethanol blended fuels brought increased concerns with water. Water has always been a concern, but ethanol exacerbates the potential problems. The two most pressing issues are phase separation and accelerated fuel system corrosion.

Phase Separation

Ethanol is both hydrophilic – easily dissolves in water and hygroscopic – water absorbing. (Jain) (F. John Hay) Water is always present in fuel at some level, often suspended in the ethanol blended fuel until it becomes heavy enough to drop out. Ethanol and water are miscible. (Helmenstine, 2017) That is, they dissolve in each other.  Ethanol is also lighter than conventional gasoline so it remains suspended in the fuel unless enough water bonds to it. Because water is heavier than fuel, with enough volume, it will drag the ethanol to the bottom once enough is present. Research shows it only takes .398% water in fuel for phase separation to occur. (F. John Hay) At saturation the water and much of the ethanol separate from the fuel and drop to the bottom of the tank. This is phase separation. Because ethanol is used to raise octane, the fuel above the phase layer at the bottom of the tank is now substandard. Fuel can also remain partially phase separated. This happens when enough water enters the fuel but has not reached saturation. During this stage, fuel can become hazy often clogging filters and shutting down engines.

It does not take much water to cause fuel to phase separate. Less than 20 gallons of water in 5,000 gallons of fuel will result in phase separation. Tank monitoring systems may not be able to detect that small amount and water finding paste can be difficult to read if this is the method used for identifying water in fuel. The only sure way of determining water in fuel is to take a good bottom sample of the fuel. Bottom sampling is the first defense against phase separation and will be discussed in detail later.

How does water enter a tank system? To name a few through fuel delivery, condensation, leaky caps or seals and holes in tanks or lines. The speed at which water enters the fuel can determine how quickly water becomes dissolved or emulsified. There are three common forms of water found in fuel. The most common is dissolved water. Because fuel is never 100% dry, it usually contains small amounts of dissolved water. Small amounts of dissolved water will not cause fuel to be cloudy and normally do not present a problem. Rapid flowing water enter a storage tank or rapid agitation will result in instant absorption resulting in emulsified water in fuel. A slow leak may take weeks to show up in the fuel. (Jain) Depending on the amount of water, the fuel may range from dissolved to emulsified. Free water is the form found on the bottom of tanks and is commonly found during phase separation. When dissolved water by volume becomes heavy enough it drops out of the fuel, settling to the tank bottom. System inspections are important to minimizing water issues and can often catch a problem before it becomes unmanageable.

Phase Separation Remediation

Can phase separated fuel be remediated? The simple answer is yes. Most phase separation can be corrected, although if there is a catastrophic event that causes large volumes of water to enter the fuel, the alternative may be disposal. There are a few simple steps to correcting phase separation.

  1. Determine the volume of phase at the bottom of the tank. This can be accomplished by using a fuel sampler. First take a sample on the very bottom of the tank, then at 1 inch increments until you determine where the phase ends and the fuel begins. There is a definite difference in the phase layer and the fuel layer on top (see photo). After determining how many inches of phase you have in your tank, you will know how much needs to be pumped out. Once the ethanol drops out of the fuel and forms a layer on the bottom of the tank, it cannot be reintroduced into the fuel. It must be properly disposed of with the water and contaminants.Ethanol phase pic
  2. Pump off water/ethanol phase and properly dispose of waste. Take bottom samples from the lowest accessible point in the tank to verify you have removed all of the phase before moving on to the next step. Keep in mind that it may be necessary to remove the STP pump for proper access to the lowest point in the tank. It is important at this stage to verify. It is also important to refrain from stirring the fuel too much. Stirring can cause emulsification.
  3. If available, use a filtration system that has coalescing and water separation capability to remove any remaining dissolved water. It is likely that some water remains and needs to be removed. Remember not to stir the fuel during filtration. The suction hose should be placed on the bottom of the slowest access point in the tank and the return should be above the fuel level in order to minimize any unnecessary agitation. Speed is not your friend when removing water from ethanol enriched fuel. Moving the fuel across the filters at a slower velocity will allow for improved water removal. Once the water has been adequately removed, the fuel octane level will need to be tested.phase tank diagram
  4. If phase separated fuel was 87 octane E10, it is possible to blend 93 octane E10 fuel at a ratio of 1:1 to correct the octane level in the fuel. For example, if you have 3,000 gallons of regular remaining in the tank, blending 3,000 gallons of 93 octane premium fuel should correct the octane deficiency. Always verify octane through testing once blending is complete. If the phase separated fuel was 93 octane E10, then the fuel should be usable as 87 octane fuel. Again, octane testing should be completed to verify results.


A second problem attributed to ethanol is corrosion – specifically microbial influenced corrosion or MIC. (Charles H.D. WIlliamson, 2015) Fuel deterioration has been documented since 1895 and accelerated deterioration since 1994. (Passman, 2013) So what has changed and why is corrosion such an issue today? Since the mandated use of ethanol, MIC has increased and become a serious problem. MIC costs the United States an estimated $50 billion per year in damage. Oil production, transportation and storage are all affected. (Institute for Corrosion and Multiphase Technology, 2018) In the most recent research, accelerated corrosion has been associated with the presence of ethanol in fuel. (U.S. EPA, 2016)

Tank Corrosion

corrosion inside tank

Water must be present for there to be microbial growth. Because ethanol is both hydrophilic and hygroscopic, ethanol blended fuels are more water soluble. In other words, water is more easily dispersed in fuel. Condensation is more easily absorbed. It is also thought that ethanol serves as a food source for microbial growth. (Charles H.D. WIlliamson, 2015)

The combination of water and ethanol serve as the perfect breeding ground for microbes. These hydrocarbon utilizing microbes produce acids. The most prevalent, Acetobacter produces acetic acid. Once the colony gains control of a fuel system, corrosive growth accelerates. Unlike typical corrosion that can take years to seriously damage a fuel system, MIC can form overnight and severely damage a system within months. Costly damage has been seen in fuel systems less than six months old.

Sump Corrosion

sump corrosion

How does the damage occur? A microbial colony begins to grow when water is present and feeds on the hydrocarbon producing an acidic byproduct. This acid will lay on the bottom of the tank and remain suspended in the fuel with any water that may be present. The combination of water, microbes, acids and deteriorating fuel form a biomass. “At the fuel-water-tank interface, all of the necessities of life are present: a carbon source, water, an electron donor (the hydrocarbon/ethanol blend and/or metals in the tank), and an electron acceptor such as O2 or previously oxidized metal (e.g., rusted steel).” (Charles H.D. WIlliamson, 2015) Even cathodically protected stainless is susceptible to corrosion. Carbon steel definitely proves no match.

As the biomass grows and accumulates on the tank bottom, an acidic off-gassing is common. The vapor fills the tank and enters the dry spaces within the fuel system. Corrosion in submerged turbine pump (STP) sumps is often a result of MIC.


While ethanol is the catalyst to an abundance of problems, there are some simple answers. No doubt phase separation and corrosion present challenges to the industry but neither are insurmountable. For both of these problems the common denominator is water. Neither phase separation nor MIC are an issue without water. If you can keep your fuel dry, then neither are an issue. All it takes is a little management.

Fuel Quality Management (FQM) is the buzz phrase that seems to be taking front stage in the battle against ethanol issues. Most realize that fuel will not manage itself. Today’s fuels need to be managed for quality. FQM is about reducing risk and limiting problems associated with water. A few simple steps are all it takes.

  1. Regularly bottom sample the fuel. Because of the potential for human error and the possibility of weather related water issues, fuel should be sampled monthly at a minimum. Ideally, bottom sampling should be done with every new load of fuel or weekly. If you do not have a bottom sampler, purchase one. They are easy to use and become the first line of defense. The diagrams below show how easy a sampler is to use. Once a sample is retrieved, it can easily be emptied into a clear sample jar for viewing.tank sampling diagram
  2. Test fuel on a quarterly basis for water and bacteria or more frequently if water is present. If bacteria is detected, administer a quality biocide to kill microbial growth associated with MIC.
  3. If water is present, immediately remove and properly dispose of it. It is imperative to keep the fuel as clean and dry as possible. If the fuel has degraded or phase separated, hire a fuel specialist to clean your tank and fuel or purchase a cleaning unit to maintain your own fuel.
  4. Clean your fuel and tanks when needed. All of the problems associate with phase separation and MIC are due to water and contaminants getting into the fuel.
  5. Do a monthly inspection of your fuel system to determine any deficiencies. If found, have them repaired as soon as possible.


Ethanol blended fuels present challenges but are not impossible to deal with. Maintaining clean, dry fuel is the most important aspect of avoiding problems like phase separation and corrosion. Professionals like the ones at Dixon Pumps can help provide answers to problems you already have or programs and equipment to limit the challenges you are presently faced with.


Charles H.D. WIlliamson, L. A. (2015, June 20). Applied Microbiology and Biotechnology. Microbially Influenced Corrosion Communities Associated with Fuel-Grade Ethanol Environments, pp. 6945-6957.

  1. John Hay, I. M. (n.d.). Ethanol and Water Contamination: Results and Observations. Lincoln: University of Nebraska.

Franklin Fueling Systems. (2012). Why Phase Separation Occurs and What You Can Do About It. Madison: Franklin Fueling.

Helmenstine, A. M. (2017, March 8). Miscibility of Fluids. Retrieved from ThoughtCo.:

IER. (2016, May 24). Latest Analysis. Retrieved from Institute for Energy Research:

Jain, S. (n.d.). Ethanol-Water Phase Separation White Paper. Veeder-Root.

Passman, F. (2013, February 26). Microbial Contamination and Its Control in Fuels and Fuel Systems Since 1980 – A Review. International Biodeterioration & Biodegradation, pp. 88-104.

Renewable Fuel Standard (United States). (2018, February 21). Retrieved from Wikipedia:

Renewable Fuels Association. (2011). Fuel Ethanol Industry Guidelines, Specifications and Procedures. Washington: Renewable Fuels Association.

Russ College or Engineering and Technology. (2018, February 22). Institute for Corrosion and Multiphase Technology. Retrieved from Ohio University:

U.S. EPA. (2016). Investigation of Corrosion-Influencing Factors in Underground Storage Tanks with Diesel Service. Washington: U.S. Environmental Protection Agency.


Fuel System Inspections


Despite all of the advances in fuel system technology, regular physical inspections are necessary and required in most areas. The EPA publishes a UST Manual that covers the operation and maintenance of underground storage tanks. Broward County publishes Your Florida Petroleum Storage Tank Facility Inspection Guide that provides valuable information and guidance on what to look for when inspecting a fuel system. Regardless of where your system is located, both of these publications are helpful.

Part of the inspection process includes identifying water and corrosion problems. If they are present, then further investigation is required. Both indicate a potential problem with fuel quality. Simply adding fuel sampling to your inspection process can help identify and reduce serious issues. Purchase a bottom sampler from Dixon Pumps and start sampling your fuel today.

Noting water and corrosion issues without acting upon the problem will allow continued deterioration of your system. Once found, it is important to identify where the problem originates.

Bottom sample your fuel monthly – at least. If water is present, have it pumped out immediately. Consider using a biocide to protect your system from microbial infection. Microbes are a main source of system corrosion. Water is where they live. Keeping your system clean and dry is essential to reducing corrosion.

Microbial Influenced Corrosion

Microbes are living cells. There are two broad categories – aerobic and anaerobic. The majority of microbes affecting fuel are aerobic. That means they need oxygen to survive and multiply. Today’s highly oxygenated fuels supply the need. The process of removing sulfur actually adds oxygen to the fuel. Water contains oxygen, is necessary for microbial growth and is always present in fuel. It is virtually impossible to keep water out. As a result, microbial contamination is almost certain.

Microbes live off fuel. They are “hydrocarbon utilizing microbes – bugs” or humbugs as they are commonly known. They live in the suspended water, water vapor and water layers in the fuel. As they eat fuel, they produce acidic byproducts. Commonly found in fuel, acetic acid is a low-level acid that destroys metal in both the wet space of the tank and the dry space and vapor areas of the tank system. The result is corrosion. Other commonly found acids are formic acid, propionic acid and lactic acid. While there are others, these are the most prevalent.

All of the acids found in contaminated fuel cause corrosion, thus the term microbial influenced corrosion or MIC. All metal that is exposed both in the fuel and in the vapor space are susceptible to corrosion. MIC is a direct result of unmanaged fuel systems. Fuel cannot go unmanaged. Water levels must be continually monitored and immediately removed when found. Fuel sampling should be done on regular basis to identify the presence of water and other contamination. Fuel and tank cleaning are also a regular part of fuel management. Without a program in place, MIC will be a direct result.

What are the warning signs of MIC? For the fuel system owner, the signs are many. Below are some of the major warning signs:

  • Premature dispenser filter replacements
  • Corroded dispenser filters
  • Dispenser meter replacements due to corrosion
  • Corroded STP components
  • Frequent or repeated proportional valve replacement
  • Slow flow issues
  • Premature or repeated hanging hardware failures
  • Leak detector failures
  • Shear valve failure
  • Line and tank failure
  • Probe failure
  • What are the warning signs of MIC in engines and equipment?
  • Fuel injector failure
  • Faulty high pressure pump
  • Exhaust smoking heavily
  • Low compression
  • Engine runs rough at lower RPM
  • Engine does not start or is hard to start
  • Engine fails under load
  • Knocking or pinging issue
  • Fuel pump failure
  • Fuel filters clog prematurely or repeatedly
  • Fuel line failure

Whether a fuel system or an engine, the problem with MIC is serious and costly. Corrosion represents the single largest expense in the US economy, 6.2% GDP. For the fuel system owner, the liability of a potential fuel release is very real if fuel quality is not maintained. For the engine owner, failure is common. It has been noted that 90% of generators do not start or stop shortly after starting during an emergency. Over 75% of those engine failures are due to bad fuel.

Mobile Fuel Cleaning

There are numerous manufacturers and assemblers making fuel filtration equipment. What makes a filtration unit superior? Four criteria determine superiority.

It must be safe. Safety is first and foremost. Does it have a safety shut-off switch clearly marked and easily accessible?  Does it have both pressure and vacuum gauges that are in clear site while the system is in operation?  Are grounding reels and a grounding rod included? Are safety instructions understandable in the operations manual? Consider the kind of fuel you will be cleaning. Do you need explosion proof or intrinsically safe? Do you know the difference between the two? How important is it? Built-in safety components make some units better. Look for safety factors when researching which unit you will purchase.

Ease of use is essential. If a cleaning unit is too difficult to use in the field, then problems will arise. Are there too many controlling factors like valves and connections?  The simpler, the better. Manufacturing equipment that is easy to use does not happen accidentally. You want tanks and fuel clean, but you do not want it to require a rocket scientist to operate the equipment. Are the gauges, shut-off switch and valves easy to access, clearly labeled and within easy reach? Can one person safely and efficiently operate the unit fs2bwith minimal effort? Before buying a system, think about its operation in the field. Ask yourself, “Is it easy to use?”

How cost efficient is the equipment to operate? Does it require special filters or odd sized consumables? Does the pump and motor require a lot of maintenance? Is it built to last? Make sure you understand the cost of all consumables and be warry of any company that cannot clarify how much it costs to operate. Look for options like mesh filter housing inserts to use in place of bag filters.  Also, be aware of the high maintenance cost of pump types like air operated double-diaphragm pumps. Positive displacement pumps like the Dixon BladeMaster pump will cut maintenance and downtime costs considerably.

How flexible is your system? Can it only clean one type of product? Flex filtration is a significant advantage. Purchasing a cleaning unit that is capable of filtering all fuels makes sense. Make sure the unit will filter all of the products you need it to.  Also, ask yourself can it clean tanks and filter fuel if the need arises.  Most mobile units can do one or the other but not both.

Make a purchase that is safe, easy to use, cost efficient and flexible. Check out Dixon Pumps mobile cleaning and filtration line of products.



Tank Cleaning vs. Fuel Polishing


Tank cleaning and fuel polishing are two different processes. The question often asked, “Which one is better?” Are there any advantages to one over the other? Cost can be a determining factor as well as site downtime, if any. Tank cleaning is generally more expense. It usually requires fuel be removed and a chemical agent applied during cleaning. Once the tank cleaning process is completed, the old contaminated fuel is filtered back into the tank or new fuel is delivered. Either way the costs are higher than simply polishing fuel in place.

Opponents on either side of the cleaning and filtration industry will argue their points, but the solution is often determined by cost of service and downtime. Let’s be honest, for many tank owners cleaning versus polishing is a matter of economics. If the only economically feasible solution is to polish the fuel – then do it. It is better than leaving contaminated fuel in the tank. Ignoring the problem will only increase the cost of ownership.

However, there are times when a tank is so contaminated that it requires a tank cleaning with pressure and chemicals. Having been in the field cleaning tanks and filtering fuel for years, I have found around 20% of the tanks serviced needed tank cleaning in addition to fuel polishing.

Welcome to Dixons CleanFuel Blog

before and after sampleIn 2016, the EPA released their investigation on corrosion. In it, they say “corrosion increases servicing and equipment maintenance costs.”  For the power generation industry, this can mean increased maintenance by as much as 30%.  In the same study, they observed 83 percent of the inspected diesel fuel tanks had moderate to severe corrosion and less than 25% of the owners had any knowledge of it.

Cummins notes that the “wear of internal parts of the fuel system will decrease the life of the components and may even cause malfunctions that could result in severe damage to the other engine components.”  The picture above shows injectors pitted by corrosion caused by bad diesel fuel.  Diesel fuel is more susceptible to degradation than a decade ago.  Knowing the problems associated with diesel fuel creates a serious dilemma for every tank owner, especially those associated with backup power generation.  It is more important now than ever before to have in place a fuel quality management program.  A good program will include:

  1. Monthly bottom sampling of fuel.
  2. Quarterly fuel testing of samples.
  3. Immediate removal of any water present.
  4. Proper use of corrosion inhibitors and biocides.
  5. Yearly tank and fuel cleaning.

Without a fuel quality management program, you will have higher maintenance costs and possible liability issues because of damage caused by bad fuel.  Additionally, fuel economy can suffer by as much as 25%.  When Hurricane Sandy hit the Northeast, backup generation failed because of bad fuel.  Almost 75% of generators either failed to start or stopped shortly after startup.  Ninety percent of those that failed were due to bad fuel.  Fuel quality management is an absolute must.  Our CleanFuel blog is dedicated to bringing you the most up-to-date information on fuel mainenance issues and solutions.

“Bulk storage diesel fuel requires full filtering every six months to one year” Caterpillar