Initial free practice at Istanbul Park had to be red-flagged briefly on Friday morning when some of the artificial carpet-like turf came loose on the exit of turn one.
The action resumed after marshals pulled up the offending 'grass', and by the end of the 90 minute session, Williams' Nico Rosberg emerged with yet another practice scalp.
"Yeah, well, it doesn't count because we just run less fuel than everybody else," the German had explained earlier in Turkey.
Lewis Hamilton trailed the 23-year-old's pace by three tenths of a second, while Jarno Trulli showed that Toyota may have recovered from its Monaco slump by setting the third best time.
Consecutive three-time Turkey GP winner Felipe Massa was fifth, while the fastest Brawn was the one driven by Rubens Barrichello in ninth. The BMWs were 16th and 17th.