Please everyone have a good read of these links to understand the background of bedding in piston rings to a honed cross hatched cylinder bore.
Yes this is written from a motorbike perspective but the same principles apply to a WRX EJ engine.
http://www.mototuneusa.com/break_in_secrets.htm
http://www.rexnet.com.au/forum/index...pic=63909&st=0
Taken from mototuneusa site:
Q: If break- in happens so quickly, why do you recommend using petroleum break - in oil (mineral) for 1500 miles ??
A: Because while about 80% of the ring sealing takes place in the first hour of running the engine,
the last 20% of the process takes a longer time. Street riding isn't a controlled environment, so most of the mileage may
not be in "ring loading mode". Synthetic oil is so slippery that it actually "arrests" the break in process before the rings can seal completely. I've had a few customers who switched to synthetic oil too soon, and the rings never sealed properly no matter how hard they rode. Taking a new engine apart to re - ring it is the last thing anyone wants to do, so I recommend a lot of mileage before switching to synthetic. It's really a "better safe than sorry" situation.
J