Good explanation. Thanks. Makes sense.

William

>
> In a message dated 4/27/02 6:01:07 PM, developtrust@COX.NET writes:
>
> << Like I said it is most likely a myth like needing to rotate radial
tires
>
> only front to back. We now know that we can rotate radial tires any which
>
> way and I believe we can break an engine in better with synthetic oil. >>
>
> Ahem! There is no reason to invoke superstition or animal sacrifice (i.e.
> belief) to explain or interpret well understood technical processes. The
> break-in process involves bringing the surface finish of the cylinder
walls
> and the piston rings to a compatible level (RMS roughness modulated by
> differences in the Young's Modulus for the two or more different
materials).
> This is accomplished in three generic ways:
>
> 1). Add an abrasive (Al2O3, SiC, aluminosilicates, particulate carbon
etc.),
> mix with good dispersing lubricant and polish away. Works poorly with
modern
> engines and neanderthal consumers.
>
> 2). Assemble the engine, provide a lubricant with adequate or marginal
film
> strength properties, but with extensive dispersant additives. Run engine
for
> break-in time. Variable speeds and load conditions are needed to get the
> broadest surface finish match between ring and cylinder wall. Here, low
film
> strength oils are by definition paraffin or natural stock based. True
> break-in oils have very poor film strength and are heavily sulfurated for
> good capture of microparticles. These microparticle suspensions can lead
to
> extensive wear if the lubricant is not changed out in time.
>
> 3). Using current (read here expensive) machining and polishing
techniques,
> prepare the cylinder bore so that at the end of machining (multiple
rebore,
> reaming and polishing, followed by anneal and polish) the ring and wall
> combination are as well matched as would be achieved after optimal
versions
> of step 2. Higher ticket, low volume manufacturers (Porsche, Lexus,
others)
> use this approach and can afford to deliver their product with high film
> strength oils (read synthetic here) and forgo the break-in ritual.
>
> So ---- use synthetics from the start in a mass market vehicle (VW, Audi,
> etc) and the surfaces will mate in 4 to 15 times the net piston surface
> lapping (translates as 4 to 15 times more miles for break-in with
synthetic
> oil vs. natural stocks). Use synthetics to break-in a remanufactured block
> from a rebuilder - we could go to Europa and Titan and return before ....
>
> No myth, no legend, just engineering, tribology and materials science.
After
> all we are in the 21st century!
>
> Frank Grunthaner