geo wrote on 01/19/08 at 16:13:24:Don't use Amsoil for break-in!
Use the dinosaur oil for the first 40 hours or 1500 miles, then switch to Amsoil. Amsoil greatly reduces friction and will not let the rings seat properly. Amsoil greatly reduces friction and wear and the heat created by friction. Go to their website where they give you the testing results.
Ok, I've had some time to research now, here's what I found...
In a new engine, there are microscopic "burrs" and ridges on machined surfaces. Low quality oil causes these burrs to shear off. This creates the affect of faster "wear in." The two bad things that happen as a result are:
1) The tiny metal flakes flow in the oil stream until caught by the oil filter or oil change depending on size. This creates scarring of other surfaces.
2) Hardness and density of machined surfaces is decreased in the long run.
Using a very high quality oil for break in has a few effects as well:
1) Break-in takes longer
2) Burrs are folded into the machined surface or compressed with less "shear-off"
3) Final density and hardness are higher in machined surfaces
Conclusion? Contrary to conventional wisdom and my own practice...using the highest quality oil available for break-in makes good sense.