dave williams
(RIME autos)  03-25-92
- -> I noticed, after checking my oil the other day, that the very tip of
  -> the dipstick had a white creamy substance on it. Just a small amount,
  -> and the rest of the stick had the normal oil covering on it. What
  -> could this be?
- It's water.  Actually, water/oil emulsion.  The inside of the crankcase
  has condensation on humid, cold days, and the water gets mixed into the
  oil when the engine starts.  This water/oil emulsion is corrosive, and
  much of a modern oil's additive package is anti-corrosive gunk designed
  just to control it.
-  You usually see the white gunk in engines that are driven for short
  distances without being fully warmed up.  If you're near the time for an
  oil change, do it.  You can prevent or minimize the gunk by making
  occasional longer trips (half an hour or so) to boil/evaporate the water
  from the oil.
- There's also the possibility of an internal water leak from a gasket or
  crack, particularly since your rebuild is relatively fresh, but chances
  are it's just condensation.

dave williams
rec.autos.tech  05-26-93
- Unless you have a problem, the oil should never get scorched. What is
  happening is, the oil changes color as the additive package "wears out."
- Your major contaminant in motor oil is plain old water, which comes
  from condensation when the engine cools off.  The water reacts with the
  oil when the engine warms back up, causing the formation of various
  acids and spoogy byproducts which are totally gross when you open the
  engine up, plus they don't lubricate too well.
- Modern motor oils are 20 to 40 percent "additives" by weight.  Most of
  this stuff is dedicated to absorbing water and turning it into something
  less harmful.  Some are wear enhancers, etc.  They all change color as
  they get older.  By a fluke of chemistry, a majority of them turn black.
- Black oil isn't necessarily a sign the oil has to be changed, though.
  Some brands turn black soon after they are poured in.

[email protected] (Dave Williams) 
rec.autos.sport.tech  6 Aug 95
- -> particulate loading capacity for abrasive and acidic species, but
  -> water is not a problem for either oil.
- Water from condensation is a problem in many parts of the country - the 
  southeastern states typically have high humidity and large temperature 
  swings inducing condensation in the crankcase.  My Yamaha has a glass window 
  in the side of the crankcase; some mornings the oil is almost white, though 
  it clears quickly once the engine reaches operating temperature. 
- If you go long enough without changing the oil and the engine never reaches 
  a high enough temperature to boil the water off (typical of many older cars 
  used for short trips) the water and oil will react to form acids, which will 
  eat the bearing shells. 
- -> So your water pump will operate less and the overall average temperature 
  -> will be lower (the temp at the coolant channels constant, but the temp at 
  -> the cylinderwalls lower (Diriclet boundary value problem). 
- I don't know who Diriclet is, but your water pump is turned in a fixed ratio 
  to the crank speed.  It operates all the time.  I don't know of any 
  exceptions to this for land vehicles; if you know of one I'd like to hear of 
  it. 
- Most cars use a poppet valve restrictor in the water path.  When the engine 
  is cool, the valves closes, restricting water flow.  This in turn increases 
  head pressure at the pump, which takes more power to turn the pump. 
- Your comment about temp at the cylinder walls being lower doesn't make sense 
  in context. 
- -> an effect anyway since friction is not the largest heat producer nor
  -> is lower oper. temps the reason for using synths.
- Not the entire reason, but a valid one.  Oil temps >300F are not 
  tremendously unusual in American Sedan racing, to give one example.  I have 
  observed factory Ford bearing shells begin to "sweat" globules of metal at 
  slightly over 300F while baking moly coatings. 
- -> Hum. I am a scientist who has worked in tribology
- Great.  However, it wouldn't hurt to learn a little more about engines.