Here's a story that might help the more inexperienced home 
mechanics(like me!):
Gave the car oil change on 7/1.  Let sit(w/o starting)until 7/7.
Start on 7/7, and knocking like crazy.  Let idle for 5 mins and 
only a little quieter.  Take around town for 2 miles, and 
finally works itself out.  
My 2 cents(sense): after you change the oil, drive it for 5 mins
Otherwise , it could lead to oil starvation.