Hey guys I'm finally getting to the replacement of my steering rack that has been disabled for two years.  I am replacing with a known good used unit (I've already weighed the pros and cons of this route), I have new bushings, tire rod ends, upper ball joints (they're torn) and pump filter.  I plan to do a thorough flush of the system.  Here's my question, I am contemplating using Mobil 1 synthetic (based on the endorsement of Dennis Haynes),  I am cheap though and it would kill me to waste all that synthetic fluid.  Are the conventional and synthetic fluids compatible?  I was thinking I could flush with the cheap stuff and add the Mobil 1 once I purged a decent amount.  
 
One other thing there are notches on the rack that indicate the center steering right? I'm going to scrub reservoir before filling and flushing and I know I'll need an alignment when I'm done.  Will the alignment shop center the steering if I booger it up a little?
 
Ryan