I just switched to Amsoil Series 2000 fully synthetic motor oil and
that terrible cold start-up engine grind and noise is greatly reduced. I would say it's reduced by %50 or more, it's almost not noticible.
My P5 has 7500 miles on and it feels smoother and quieter with Amsoil in.

 

what oil did you use before?

 

I did use Castrol 10-30 at first until 1500 miles than I did oil change staying with Castrol 10-30, and at 4500 miles I switched to Pennsoil/Amsoil 7500 series, mix 3:1 proportion and finally at around 7500 I'm running on 0-30 Amsoil series 2000 (recommended for cars using 5-30 or 10-30). It works great.