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Here's an article I read recently about engine break-in. Seems even the manufacturers disagree....
Using synthetic-oil in engine break-ins
By Road & Track, Technical Correspondence Column, July 2000 issue
"Many readers have questioned us on engine break-in procedures when using synthetic oil. Conventional wisdom has it that a new or freshly rebuilt engine should be broken in using mineral oil, then, once enough mileage has accumulated to ensure rings and cylinder walls have lapped themselves into harmony, synthetic oil can be used.
Readers have correctly pointed out that several major brands come from the factory with synthetic oil, among these being Corvette, Mercedes-Benz and Viper. How can these engines break-in if run on synthetic oil from day one, they ask?
To find out, we spoke with Mobil and Redline Oil companies for their take on the synthetic break-in question. Mobil's response was that engines break-in just fine on synthetics, and that any wear point in the engine significant enough to be an interference, and thus susceptible to rapid wear, would be a wear point no matter what lubricant is used.
Redline, on the other hand, has found it best to recommend a mineral oil break-in. Occasionally an engine will glaze its cylinder walls when initially run on Redline, they say, so by using a mineral oil for 2000 miles, verifying there is no oil consumption and then switching to the synthetic, glazing is eliminated.
Cylinder-wall glazing is not a deposit left on the cylinder wall, but rather a displacement of cylinder-wall metal. This happens when the high spots of the cylinder wall crosshatch are not cut or worn off by the piston rings, but rather rolled over into the valleys or grooves of the crosshatch. This leaves a surface that oil adheres to poorly, against which the rings cannot seal well. Compression is lost and oil consumed, and the only cure is to tear down the engine to physically restore the cylinder-wall finish by honing.
Why is glazing not a problem for the major manufacturer? Because they have complete, accurate control over their cylinder-wall finish and ring type. Redline deals with a huge variety of engines and manufacturers, both OEM and from the aftermarket. Cylinder-wall finish and ring type thus vary greatly, and glazing can therefore occur, albeit rarely."
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