I don't know if this is a known fact, but I know some people recommend using non-detergent oils for breaking in a motor. You have got to be REAL careful with non-detergent oils. Modern motor oil as we know it is rated SL or SM--it has detergents, anti-foaming agents and alot of other additives that modern motors NEED to survive. Some of the non-detergent motor oils I have seen are rated SA--meaning not only do they not have detergents but they have NOTHING added to them!! They basically take the oil out of the ground, filter it and put it into the bottle. You can usually tell if a non-detergent oil is rated SA because it will say (I am not joking) "this motor oil is NOT suitable for cars manufactured after 1939" or 1930 (can't remember) I once spun a bearing in a motor at idle (motor had good oil pressure) and the ONLY reason I could think that the bearing spun is because I used Castrol non-detergent motor oil. The Castrol non-detergent motor oil has non "S" rating whatsoever on the container--which leads me to believe that it is an SA (plain oil) rated oil. I am not saying all non-detergent motor oils are like this, but why take the chance? Just run regular Castrol GTX to break in a new motor-and everyone will be happpy. Modern cars NEED oils with additives--maybe a new motor would be better with a non-detergent oil, but its hard to tell if the oil is missing other important additives that are necessary for modern cars.