Phase Separation describes what happens to gasoline containing Ethanol when water is present. When gasoline containing even small amounts of Ethanol comes in contact with water, either liquid or in the form of humidity; the Ethanol will pick-up and absorb some or all of that water. When it reaches a saturation point the Ethanol and water will Phase Separate, actually coming out of solution and forming two or three distinct layers in the tank.

REQUIRED READING- http://fuelschool.blogspot.com/2009/02/phase-separation-in-ethanol-blended.html

Also -

Further the federal government currently subsidizes Ethanol with a $.51 per gallon tax credit that goes to the refiners or blenders. With E-10 this provides those refiners and or blenders with a $.051 per gallon subsidy on every gallon of gasoline that they sell.

In many cases we have seen gasoline containing more than 10% Ethanol. We test regularly and have seen fuel containing 12%, 13%, and even 14% Ethanol while the pump shows only 10%. Increasing the amount of Ethanol increases the refiner/blenders subsidy and profit while further lowering your fuel economy.

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Yep I deal with phase separation at work all the time.  even with something like stabil in the tank it wont phase separate but you can still smell the ethanol has gone bad.

Which has me wondering on vented gas tanks that are vented straight to the atmosphere such as on Fords of this era with a fuel tank vent that vents behind the license plate if humid areas such as Houston will result in a reduction in octane in a shorter period of time.  That is why I been running the stabil 360 which says it stabilizes ethanol but I just haven't found anything concrete on if it makes much of a difference other than preventing phase separation or not.

Wish the cold front wasn't still moving through here I would like to drain my tank today and get some fresh 93 octane and put in, that is if my local gas station is selling 93 octane and it just isn't regular old 87 being sold as 93.


1956 Ford Fairlane Town Sedan - 292 Y8 - Ford-O-Matic - 155,000 mi

...humid areas such as Houston will result in a reduction in octane in a shorter period of time...

Yes as the octane additive(s) is in the methanol-




And the same will happen in the CARB fuel bowl(s) as they are open vented also.

I think the first line of defense (other that non-ethanol gasoline or EVAP) is to have a drain at the bottom of the gas tank to draw water off at intervals,

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Well I finally got some good weather to get the gas out and put fresh in.  The gas that came out it wasn't bad but it was yellowed none the less which means it is aged quite a bit.

I drained as much as I could out and put just 5 gallons of straight 93 octane in the tank.  Fired the car off and ran a bit wonky as it was coughing every now and then in the exhaust with a miss felt in the body.  After running for a bit the old gas got out of the carb and the fuel pump to the point that it was running on fresh 93 octane.  I power braked the car and hit the gas a bit reving it to see if I could force it to spark knock for a bit cause it would spark knock for a split second before after I enriched the fuel mixture on the accelerator pump to the winter setting.  I did it this time and I physically heard no spark knock at all.  I didn't drive the car but I will give it a try when the weather clears up again and see if its still knocking when accelerating for driving.  I think I might have resolved it cause before I could hear a faint knock in the engine when running with no load it was probably the old gas pinging on me cause now I don't hear it, I just hear the rockers clicking faintly.


1956 Ford Fairlane Town Sedan - 292 Y8 - Ford-O-Matic - 155,000 mi