I stumbled across this cool Shell Rotella site which provides 77 Q&A topics on motor oils. A sampling:
#22. "The term 'break-in oil' is a relic from the old days...With all the advances in parts metallurgy and machining techniques, manufacturers can break in their engines with fully formulated, off-the-shelf engine oil."
#24. "You should also be aware that engines typically go through a period of adjustment when making the transition from one oil to another. Because brands are formulated with different additives, a new brand may act differently than the old one at first. Increased oil consumption and leaking seals are common adjustment problems."
# 73. "Remarkably, this shearing can sometimes occur within several hundred miles of driving, and cause oil pressure to decrease. Usually the decrease isn’t enough to worry about, especially if you start with high viscosity...Some oil makers hedge viscosity on the high side to cover their oil pressure downside. You pay for that with a little more fuel burn."
#45. "Synthetic transmission and gear oils also enable you to extend the oil change interval up to five times longer than a straight mineral oil."
http://www.rotella.com/qa/searchprocess.php?search=
#22. "The term 'break-in oil' is a relic from the old days...With all the advances in parts metallurgy and machining techniques, manufacturers can break in their engines with fully formulated, off-the-shelf engine oil."
#24. "You should also be aware that engines typically go through a period of adjustment when making the transition from one oil to another. Because brands are formulated with different additives, a new brand may act differently than the old one at first. Increased oil consumption and leaking seals are common adjustment problems."
# 73. "Remarkably, this shearing can sometimes occur within several hundred miles of driving, and cause oil pressure to decrease. Usually the decrease isn’t enough to worry about, especially if you start with high viscosity...Some oil makers hedge viscosity on the high side to cover their oil pressure downside. You pay for that with a little more fuel burn."
#45. "Synthetic transmission and gear oils also enable you to extend the oil change interval up to five times longer than a straight mineral oil."
http://www.rotella.com/qa/searchprocess.php?search=