I went with 5W20 in the Graphite car (in my sigline) at around 80,000 miles - it helped. I have now come to a conclusion, the way to get nicer smoother shifts in the Crossfire involves three prerequisites:

1) Put some MILES on the car, it shifted way better when it had 75,000 to 116,000 on it than when I bought it at 44,000.

2) Change the transmission fluid to Mobile 1 5W20 (It DID help)

3) Drive the car like a SPORTS CAR with a stick, not a pickup truck with a stick...