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 |
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