I have a new engine rebuild that my engine builder used Rotella T 30W (plus I added a bottle of ZDDP) for engine breakin...primarily to break in the cam. Well after 500 miles the rings never seated and has major blowby. Getting ready to do an engine diagnosis (leak down test, compression test) and probably need to pull the engine to possibly replace a bad block (??). Anyway my builder just talked to a collegue in the industry and was listing all the machining, parts etc he used and when he mentioned Rotella T he said "there's your problem"...basically he told him that he just had the same problem and Shell recently changed thier compostion to a semi-synthetic and not listing on the label. As many know you can't seat rings with a synthetic oil. Anyway I tried "talking" to my builder saying that I know a lot of people that use Rotella T for break in with no problems plus I frequent a forum that specializes in "oil" and I have not heard of this. Anybody have any idea where this guy got this info from ??