For those of you who believe putting synthetics in a new engine could cause the engine not to break-in properly, I have the following question: I have a 2003 Saturn that I switched over to M1 10W30 when it had 2000 miles on it (it has 8300 now). I religiously watched the oil level through the oil change interval (I wanted to change it at 6000 mile intervals). The oil level stayed somewhat constant from 0-4500 miles (in the O.C.I.) but then dropped rather quickly from 4500-5100 miles where I needed to add a quart. If I would change back to conventional oils for a change or two, do you think I could get the oil usage to go away (engine would wear-in properly)? The only way I could think of why the oil level dropped so much after the 4500 mile mark was if the oil thinned out. What else could cause that? I know I could run an oil analysis but I would rather not since the car is so new. Thanks.