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Miscible - acetone in petrol/oil & water?

  1. Apr 18, 2015 #1
    This refers to the addition of acetone in petrol and diesel, and the potential action on any water within the fuel.
    For interest: https://www.physicsforums.com/threads/adding-acetone-to-the-gasoline.366946/
    The above provides an interesting live understanding of the benefits to be gained...... however:

    This is primarily a question for chemists:

    We are led to believe, that by adding acetone to fuel @ 1.5 - 2.5ml/L (diesel & petrol).... the fuel surface tension is reduced, allowing improved vaporisation, resulting in increased fuel burn efficiency.
    Note: my own practical tests have shown this to be the case.
    Idle speed immediately increased (ie. increased power output from combustion)...... and deposits on the spark plug reduced significantly (meaning better burn efficiency)....... many other independent tests produce similar results.
    There is no disputing, the improved fuel burn efficiency in both petrol and diesel engines.

    Question: How is the acetone mixing with the petroleum products?

    I have read that acetone 'combines' with water (possibly creating a gel-like substance).
    But this doesn't get to the fundamentals...... which are:

    We mix 2.5ml of acetone, with 1 litre of petrol, which has an additional 7.5ml of oil also mixed in.
    Within this mix.... theoretically, there may be the presence of water, due to condensation within the fuel reservoir.

    I'm questioning how is acetone mixing....... is it chemically combining with the petroleum products to produce the decrease in surface tension....... yet it can evaporate off....... and then..... what's the difference with water.... in effect....... is this a miscible scenario, or a chemical combination...... or in fact, what is actually happening?
  2. jcsd
  3. Apr 19, 2015 #2


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    Staff: Mentor

    It doesn't combine with anything. Mixture is just a mixture.

    And no, acetone doesn't "combine" with water in any sense. They are just miscible.
  4. Apr 19, 2015 #3
    Thanks for the response....... I'm sure that you can understand the 'fog' that surrounds this additive.
    To a large extent, the people interested in this subject are dealing with physical results, and trying to make sense of them,

    The question ultimately splits into 'mixing' with petroleum products, and water (water being potentially present).
    There have been statements made, that acetone will mix with water, to create a gel/emulsion, that could create problems with injectors.

    We read such statements, but understand nothing of the chemistry....... as such statements are made vis a vis: results of presumed observation of physical reactions....
    ..... though I have no memory of any statement made, regarding 'conclusive tests' that prove this.
    (we don't even know if this statement was once made, and has then been repeated, as if a given........ like an error that, once admitted into the data; then remains).

    So from a chemistry perspective........ given that a tank of fuel might contain petrol, oil, and water........and 2.5ml/L of acetone is added.....
    .... from your statement, we presume that the acetone is now evenly distributed/mixed (as is the oil...and apparently water may be held in the oil - again 'fog'):

    We do know that combustion is affected to a greater degree than simply the burning of acetone (burn efficiency tests are quite remarkable, and cannot be attributed to the addition of 2.5ml/L as a fuel in its own right).

    So do we know what is happening?
    The overriding theory is that fuel surface tension is reduced, enabling better vaporisation of the fuel, ensuring a more complete 'fuel burn'.
    I initially added just 1ml/L of acetone...... and the change in combustion was immediate and remarkable........ this is an observed fact, simply from engine speed at tickover - performance after that is purely subjective, but not the plug colour.

    For the plug colour, I created a fuel/air mix of extreme richness, that I had previously tested, that produced a clogged 'carbon deposit covered' plug.
    With acetone added..... it was a very clean plug (though the sound [thud] of the engine was typical of the rich mix ie. as previously tested).

    Other physical observations:
    I believe that the acetone is evaporating, as after 9 days with an initial 5l fuel mix....... the tickover speed dropped, when only around 1L of fuel remained.
    I re-filled with an acetone mix.... and tickover was restored (to the setting used with acetone).

    Acetone with water (this is an interesting side issue)...... could it create a gel/emulsion?...... I have justed added acetone to water.... and no gel was created.
    Acetone with petrol/oil mix, or with diesel........ do we know why it aids the breakdown of surface tension (if this theory is the reason behind superior burn efficiency)
    is there another theory why fuel burn efficiency could be improved to such an extent?

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