> John Thrower writes:  
> 
> Hey
> 
> I was just over at the vintagvw list and there was a short discussion about 
> the type of oil used with various opinions attached.  I have used Castrol HD 
> 30 always and a one time treatment of Slick 50.  Once I used one of those oil 
> thickeners, Honey oil as I recall, without any ill effects.  In previous H2O 
> cooled engines (Honda, Datsun, GM) i've never had any problems with 
> additives.  Of course I am keen enough not to put a deposit removal additive 
> in an engine that is has oil burning/leaking troubles.  Those deposits might 
> be the only thing holding the majority of the oil in.   My question is what 
> are your opinions!, specifically about oil thickners that quiet lifters and 
> reduce oil loss. 
> 
> 
> JOHN 70 bus and looking after a friends  78 camper.
> 
> ps my bus burns oil just fine it is the 78 i'm worried about and may detail 
> at a later date ---we shall see.
> 
 
  Starting a discussion on oil and the crap we put in it is like opening a 
  true Pandora's Box. 

  There is lot's of literature available from the SAE (Society of Automotive
  Engineers) on lubricants, there was also a interesting article in Consumer
  Reports several years ago. 

  My take on oil, based on what I've read, is that the viscosity should be
  chosen according to the outside temperature at which you are starting the
  engine. This is basically what my owners manual says as well. 
  Apparently, most engine wear takes place in the first minute or so after
  the engine is started. If the viscosity of the cold oil is too thick it 
  will not have the mobility to form a protective film fast enough after being
  scraped by a piston ring or the leading edge of a cam follower. This must be
  balanced against having a high enough viscosity that adequate film strength
  remains when the engine is hot.

  One of the declared advantages of multigrades and synthetics is that the slope
  of the plot viscosity vs temperature is flatter (less thickening with 
  colder temperatures). Incidentally, for those of you who are not familiar
  with the oil rating schemes for multigrades: the first number, 20 in 20W-50
  for example, corresponds to the equivalent monograde at 0 degrees F. The
  second number corresponds to the equivalent monograde at 212 degrees F. 

  So what do I do?  Castrol GTX multigrade, 20W-50 in summer, 10W-30 in 
  winter and I mix them in spring and fall. Why not 10W-40? I have been 
  uncomfortable with 10W-40 ever since General Motors recommended against
  using back in the early '80s. 10W-40 weight oils were that last ones to
  get the CC and CD ratings (which are for diesel use, but are a measure of 
  gum and sticky deposit formation at elevated temperature). These deposits,
  I think, may be more likely to occur in some of the high temperature
  excursions experienced by air cooled engines.

  I have little experience with additives. I put some stuff in my Oldsmobile
  gargantua wagon (don't ask, I can't explain) to quiet a noisy lifter but it
  had very little effect that I could notice - the lifter was still noisy when
  the engine was first started - same as before.

  Dave Kautz