Championship leader Nico Rosberg set the pace for Mercedes in an opening Chinese Grand Prix practice session that was twice stopped for red flags on Friday.
Rosberg’s benchmark time of one minute 38.037 seconds was over a tenth faster than second-placed team mate Lewis Hamilton’s best, but neither Mercedes driver had a straightforward session.
Rosberg, who leads Hamilton by 17 points in the standings and heads into the weekend gunning for his sixth-straight win, limped home with engine issues at the end of practice.
Hamilton meanwhile, already carrying a five-place grid penalty due to a gearbox change, reported struggles with "locking" problems and spun twice at turn 11.
Friday morning’s opening 90-minute session was headlined by two red-flag stoppages as Williams driver Felipe Massa and Renault's Kevin Magnussen both suffered high-speed left-rear tyre failures while running on the same soft-compound rubber.
However, Formula One’s tyre supplier Pirelli said the problems for Massa, who suffered a similar failure later in the session, were not caused by a puncture. An investigation into Magnussen’s failure was still ongoing, they said.
While Williams did not send its cars back out, there seemed to be no concern among other teams as they took to the track on the yellow-marked tyre for a frantic final eight minutes following the second stoppage.
Sebastian Vettel went third fastest for Ferrari, six-tenths slower than Rosberg, with Red Bull's Daniel Ricciardo fourth over a second back.
Fernando Alonso set the 12th-fastest time on his return to track action after being forced to sit out the last race in Bahrain on doctors’ orders due to injuries suffered in a crash in the season-opening Australian Grand Prix.
The Spaniard, who came through a medical on Thursday to take part in practice, was cleared to race on Sunday after passing another round of medical tests following opening practice.