ETHANOL PRODUCER'S DATA BASE

Ethanol/Water Solubility Table

 Ethanol is very sensitive to water with water solubility of 100% at 70˚F.

A 10 v% ethanol blend has a water tolerance of ~ 0.45% at 60˚F and less at lower blend levels The table shows tolerance of 3 comon fuel blends.

Once a gasoline ethanol blend reaches water saturation, The water and alcohol will “phase separate”  This results in a lower phase of alcohol and water and an Upper phase, of predominantly hydrocarbon fuel.

     The amount of water that the three common ethanol blend levels can tolerate, before phase separating (at 60˚F) is:

     0.20% at 5.7 V%  Ethanol,  0.33 % at 7.7 v% Ethanol,  0.45% at 10 v%   Ethanol

When water is present in a fuel tank with gasoline that contains ethanol, the water will be drawn into the fuel until the saturation point is reached.

Beyond this level of water, phase separation will cause the ethanol and water to separate from the gasoline and drop to the bottom of the tank.

If the lower phase of water and ethanol is large enough to reach the fuel
inlet, it could reach the engine and cause problems.

Phase separation, occur when water is introduced to the fuel system.

If precautions to prevent water from entering the fuel system are taken, water phase separation will likely not occur.

When phase separation occurs in an ethanol blended gasoline, the water will actually combine with the ethanol and fall to the bottom of the tank.

In two-stroke engines, the water-ethanol phase will prevent some of the blended oil from bonding to the metal engine parts. The engine may not have enough lubrication, and engine damage will result.

In the case of four-stroke engines, the water-ethanol phase will likely combust in the engine. This combustion can be damaging to the engine because the water ethanol phase creates a leaner combustion mixture, that raise the combustion temperature to a damaging level.

Also, since conventional gasoline does not absorb water, there is often a layer of water present at the bottom of filling station tanks, water being heavier than gasoline.

Since the solubility of water in both gasoline and air

Is directly proportionnal to temperature, water can enter a fuel system through condensation when the atmospheric temperature changes.