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Ten Things Delaware Tank Owners and Operators Need to Know About E-10 Gasoline


Delaware Department of Natural Resources and Environmental Control
Tank Management Branch
391 Lukens Drive
New Castle, DE 19720
302-395-2500 (phone)
302-395-2555 (fax)

  1. Corn Icon“Ethanol” is a type of alcohol, typically made from corn
  2. “E10” is a blend of 10% ethanol and 90% unleaded gasoline. Anything with more or less than a 10% concentration of ethanol cannot legally be sold in Delaware.
  3. Ethanol readily mixes with water. If you are not diligent about checking for water in your tanks and removing it, the ethanol in the E10 blend will “find” the water, separate itself from the gasoline, sink to the bottom of the tank, and cause problems for your customers’ cars. Any water intrusion problems must be fixed. No amount of water in the tank is acceptable.
  4. It is best to clean the tank before taking your first delivery of “E10”. Any sludge or particulates in the bottom of the tank will be suspended in the ethanol and can cause problems with filters and fuel lines.
  5. Since ethanol is a good cleaning agent, it will loosen scale buildup and sediment from your tanks, piping, and dispensers when you first start using it, so you may have to change the filters in your dispensers more frequently, at least at first. Filters must have pores of 10 microns or less on dispensers selling E10.
  6. E-10 LogoYou must use the correct paste to check E10 tanks for water. This is different than the paste used for the current gasoline/MTBE mix in your tanks.
  7. You are required by the Delaware Department of Transportation, Motor Fuel Tax, to label the dispensers so that consumers know the gasoline is blended with ethanol.
  8. Tank system equipment composed of certain metals, polymers and elastomers may not be compatible with ethanol. Verify the compatibility of your tank system components including leak detection equipment, sump sensors, and pumps are E10 compatible and ensure your Automatic Tank Gauge systems are properly calibrated for use with E10.
  9. Most vehicles and small engines should run fine on E10, as long as water does not enter the tank. Customers should check their owner’s manual to verify compatibility.
  10. Ethanol blends should not be mixed with gasoline containing MTBE.

Clipboard iconRecommended Tank Operator Checklist

Before First Delivery

  • Verify compatibility of tanks, piping and other equipment.
  • Investigate tank water infiltration problems and correct them.
  • Tighten all visible fittings and connections at the tank top.
  • Ensure that sump and spill containment covers prevent water from entering the tank.
  • Remove all MTBE blended gasoline from the tank.
  • Gas type coding iconsClean tanks, if necessary.
  • Install ethanol compatible 10-micron filters on all dispensers.
  • Stencil “E10” on fill pipe and access covers (see example).
  • Label all dispensers as containing 10% ethanol blended gasoline.
  • Issue alcohol compatible water checking paste.
  • Ensure your tank and piping leak detection equipment will function properly with E10.
  • Check with the Delaware Department of Transportation, Motor Fuel Tax, for any specific requirements they may have. Contact Mike Harrell, 302-744-2730


  • Check for water before initial delivery.
  • It is recommended that pumps be shut down during initial delivery.
  • Fill tank to 80% capacity. Keep as full as possible for 7-10 days.
  • Conduct a precision test of the tank system (0.1 gph leak rate) system as soon as the product stabilizes to ensure the tank system is tight and leak detection equipment is operating properly. Report any failed results to the Tank Management Branch, 302-395-2500.
  • Test for water at the beginning of each shift for the first 48 hours after initial delivery.
  • Test for water daily after the initial 48 hours. Remember – no amount of water in the tank is acceptable.
  • If dispensers appear to run slow replace filters. It is expected that filters may clog frequently for the first 1-2 months after initial ethanol delivery, longer if the tanks are not cleaned.
  • Spills and Releases must be reported and handled in the same manner as non-ethanol blended gasoline. 1-800-662-8802

Remember: No Amount of Water in the Tank is Acceptable!

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