So the other day im leaving work and its about 40-45 degrees outside and I start up my car let it run for a minute and left and saw a little bit of bluish white smoke coming out of the exhaust. currently im running mobil 1 5w30. Anything to be concerned about???

If it happened after a cold start and went away, it could be bad valve stem seal(s). A real mechanics hand held vacuum gauge, not a boost/vac gauge in the car, can help determine this.

Bump. I have this (and have had this for a few years), ONLY when very cold (like sub 30 degrees, does not happen in the spring/summer). Is this something that could cause harm to my motor? runs fine otherwise. Also, probably a b**ch of a job to replace them, right?

2004 WRX, 92k miles.