thanks for all replys,, i m just a lil worried i guess being this is my first stang i bought and had to take out complete engine and replace it with a used one with 65 thousand miles on the odometer and replaced all the compenents with brand new parts and just wanna make sure i did the right thing by putting in the break in additive in my first oil change since the motor was in and now i can just drain that oil and start putting in sythenitic oil and change every 3 months seems to be the answer everyone agrees on ? again guys thanks again and sorry to sound like a newb just rather ask a question and be safe and learn and do the right thing for my car..thanks again synthetic oil is the way i should go than ?