The second day of the AT&T Williams Jerez test would see Kazuki Nakajima take over from Dani Clos as the team continued to test both the KERS system and components for the 2009 car, the most noticeable being the rear wing. The  2009 rear wing was much higher and narrower than the 2008 design.

On what was a sunny day Kazuki would run with a modified FW30 which was also fitted with the team's KERS, the only one in the field known to be using a flywheel. Various other 2009 components were also installed on the car including the teams 2009-spec rear end which includes a heavily modified rear diffuser.

The 2009 rules allow the rear wing to be just 800mm wide, but it is allowed to be deeper and placed higher up. While the new diffuser is lower, shorter, and moved further back.

Kazuki would finish the day slowest of the eight cars present with a time of 1m:23.171, having completed sixty one laps.

Williams F1 Technical Director Sam Michael commented: “Kazuki joined the test team in Jerez today and took to the track in the FW30B interim car to continue  work on the KERS and also various new components for 2009. Kazuki will return tomorrow for day three of  the test.”