A couple more things.
Do not use ANY additive in the motor.
Use exactly 7.5 quarts with a filter. Do not just pour in 8 quarts.
Run it up in 2 gear to about 70 MPH and let off the gas as it slows down the Northstars like the sucking on deceleration that helps with the carbon. Do it 2 or 3 times in a row.
Enjoy your Ride!
Charlie

Just curious,why don`t you recommend synthetic oil in this application?

My 1999 SLS never leaked a drop until I changed it over to Mobil 1. Just my experience. We recently took delivery of a 2008 STS with a 3.6 Direct injection. Mobil 1 is required.