The preferred method for switching a tank from storing straight gasoline to storing an ethanol blend is to drain the tank and pump any water from the bottom of the tank until it is completely empty, and then add the new E85 product. When E85 is dropped in the tank, it should be filled as close to capacity as possible to minimize the effect of any small amounts of water that may remain.
An alternate method of switching a tank from gasoline to E85 storage would be to blend the existing gas with sufficient volumes of ethanol to bring the overall mixture up to the proper percentage of ethanol. For example, if a 10,000-gallon tank contained 1,000 gallons of unleaded gasoline, 7,650 gallons of straight ethanol and 350 gallons of gas (about an E95 blend) could be added to a delivery to bring the entire tank’s contents up to meet the spec for a “Class 1” E85 blend.
As always, care should be taken to remove any water from the tank bottoms, and the tank should be filled as close to capacity as possible to minimize the effect of any small amounts of water that may remain. Be sure to label pumps appropriately, using decals required by state motor fuel regulations.
With either method, some marketers take the intermediate step of adding a small amount (500-1,000 gallons) of an E10 blend to the tank so that any remaining difficulties will be discovered using a smaller amount of fuel which responds more quickly to excessive water or sludge remaining in the tank.
For a complete Ethanol Conversion Checklist click here.