No matter the oil proper break in requires high rpms...
If you cutaway a piston, ring and cylinder wall and inspect under magnification you see something
to the effect of "saw teeth"... Given that a film of lubricating oil holds the piston ring away
from the cylinder wall. Proper break-in of piston ring to cylinder wall requires that the ring rupture
or break through this oil film and make contact with the cylinder wall. During such "metal to metal"
contact, the little peaks on the ring face and cylinder wall become white hot and rub off. This
condition will continue to occur until the ring face and cylinder wall have established a smooth
compatible surface between each other. At this point, break-in is said to be relatively complete and
very little metal-to-metal contact will occur hereafter. In fact, as the break-in process
progresses, the degree of metal-to-metal contact will regress.
How do you know if break is done??? take a compression test... if your
engine shows factory compression then break in is complete... if your
engine shows less than factory compression then more break in is
require... more B.M.E.P. (Brake Mean Effective Pressure)