• Re: Milky sludge in IO-540 - which oil to use?

    From sockpuppet61@1:2320/100 to rec.aviation.owning, rec.aviation.p on Sat Jan 19 18:14:33 2008
    So far the verdict on the general engine condition (700hrs) is 100/100
    for LOP operation though !!

    Why argue with success?
    --- SBBSecho 2.12-Win32
    * Origin: Derby City BBS - Louisville, KY - Derbycitybbs.com (1:2320/100)
  • From Dan_Thomas_nospam@1:2320/100 to rec.aviation.owning, rec.aviation.p on Sat Jan 19 18:33:40 2008
    On Jan 19, 7:14 pm, sockpuppe...@gmail.com wrote:
    So far the verdict on the general engine condition (700hrs) is 100/100
    for LOP operation though !!

    Why argue with success?

    Because that water/oil emulsion is going to eat that engine. Water
    and oil eventually form acids.

    When we used Exxon oils (EE80 and EE100) we found it going milky
    like that, too. Nevver seen Aeroshell 15W50 do that. I'm wondering if
    Exxon's formulation mixes more easily with the water? I don't know the chemistry involved, but these are both detergent oils and perhaps the
    detergent Exxon uses absorbs and holds the water better. Or, more
    correctly, worse. When I worked in the machine shop we used water-
    soluble oils for metal cutting; they were just oil with soap in them
    to bind the water to the oil.

    DAn
    --- SBBSecho 2.12-Win32
    * Origin: Derby City BBS - Louisville, KY - Derbycitybbs.com (1:2320/100)
  • From Dan_Thomas_nospam@1:2320/100 to rec.aviation.owning, rec.aviation.p on Sat Jan 19 20:25:18 2008
    On Jan 19, 7:48 pm, sockpuppe...@gmail.com wrote:

    It seems weird, the water in there. It must be absorbed from the air
    during combustion. Is that it?

    Water is a byproduct of combustion, and since the piston's
    rings leak a small amount of combustion gases from the cylinder into
    the crankcase, water vapor gets in there and condenses. It's much
    worse in colder weather, much worse if the airplane is flown on short
    flights so that the crankcase and oil don't heat up enough to boil off
    that water, much worse if the rings are badly worn.
    Oil contains hydrogen, chlorine, sulphur and nitrogen
    compounds. Water has both hydrogen and oxygen. All the ingredients are
    there for various acids (hydrochloric, sulphuric, nitric) and if the
    water and oil are left together long enough they'll make them. I think
    that the presence of metal is a catalyst in the process.
    I'm no chemist. I'm an aircraft mechanic and over the years
    have seen lots of corrosion in engines, mostly those that were flown infrequently and for brief periods. My own engine suffer this. Sludge
    also seems to accumulate in such engines, and automoblies aren't much
    different here.
    The engines we fly hard every day in the flight school reach
    TBO easily and are still in dandy shape when we take them off. Very
    little corrosion inside. Very little sludge.

    Dan
    --- SBBSecho 2.12-Win32
    * Origin: Derby City BBS - Louisville, KY - Derbycitybbs.com (1:2320/100)
  • From nrp@1:2320/100 to rec.aviation.owning, rec.aviation.p on Sun Jan 20 10:38:21 2008
    From 1st year college chemistry, one pound of gasoline will combine
    with 3 1/2 lbs of oxygen (about 15 lbs of air) to give 3 lbs of CO2
    and 1 1/2 lbs of water. Some of that water (and CO2) will find its
    way into the crankcase, where the dew point of the water vapor will be
    about 180 degF. On shutdown the water vapor will condense on the
    cooling surfaces to make corrosion-causing acids.

    Car engines flush the crankcase with positive crankcase ventilation.
    That is thought to explain the considerably longer engine lives of
    cars. Some are now suggesting a ground based dry flush system for
    aircraft engines, but unless it is immediately applied on shutdown,
    I'd think the value would be limited. A saving grace for cold engines
    is that all chemical reaction rates (including corrosion) are cut in
    half for every 18 degreesF of temperature reduction.
    --- SBBSecho 2.12-Win32
    * Origin: Derby City BBS - Louisville, KY - Derbycitybbs.com (1:2320/100)
  • From Dan_Thomas_nospam@1:2320/100 to rec.aviation.owning, rec.aviation.p on Sun Jan 20 12:02:42 2008
    On Jan 20, 11:38 am, nrp <dane...@earthlink.net> wrote:
    A saving grace for cold engines
    is that all chemical reaction rates (including corrosion) are cut in
    half for every 18 degreesF of temperature reduction.

    I had wondered about that. Thanks for the figure. Now, maybe we
    need a refrigeration system for that crankcase:-)
    We could have cold-weather starting problems year-round!

    Dan
    --- SBBSecho 2.12-Win32
    * Origin: Derby City BBS - Louisville, KY - Derbycitybbs.com (1:2320/100)