I was always curious to know, what exactly teams do in FP2 long runs and find a correlation from Race data to see what kind of picture comes out that help us understand the FP2 better.
There are two things I see, which are faily obvious ones. They use 2 stints worth of fuel loads (not the full race fuel loads) in FP2. They also use one step lower engine mode.
Here is the FP2 and Race first/second stints from this past week's Bahrain race. I have used the data for those drivers who were in clean air in race to avoid DRS enabled times. Max, Charles, Sainz and Hamilton all ran without DRS first most of their first 2 stints race. There was some slip stream effect though.
Here is the Speed Trap data between FP2 and Race (Click on image).
Only Red Bull appears to use Race mode in FP2. They have another Race Mode that they used on Day 1 in testing and never used after!!! It correlates to Mark Huges said in one of his the-race.com podcast, where he said, RB found themselves quite happy on Day 1 and turned down things from Day 2 onwards. Below is the snapshot of that stint.