Here's a quick visual review of the second practice session from the 2011 Singapore Grand Prix.
First up, a summary of how the teams used the session:
Here's a very crude summary of the times recorded by each team for direct comparison.
Maybe more usefully, here's a breakdown of the laptimes by stint for a couple of the teams...
And secondly, Mercedes:
Plots for the other teams are available from the F1DataJunkie Singapore 2011 Gallery