DC literature says 6.5. Most tests I've seen have it 6.4 to 6.7.

Edmund's, and now apparently Clarkson, both have it at 7.2

Doesn't really mean much. Most of us don't do to our cars that which is needed to get optimal 0-60 times. My guess is that neither Edmund's nor Clarkson really did the optimal times.

I have the most respect for R & T. In their tests they describe exactly the technique they find for each car to get optimal times.