In many ways, yesterday's sessions posed more questions than they answered.
Max Verstappen was quickest in FP1, while Nico Rosberg crashed out. Then, in FP2, it was the German who led the way while his Mercedes teammate was sidelined by a hydraulic leak.
On the other hand, both Mercedes drivers set their best times on the soft rubbers while their rivals were on the supersoft.
Renault, which had originally intended giving only Verstappen its latest update will now have it available for all four drivers including its works drivers Palmer and Magnussen.
Ferrari was very much on the pace, though Vettel appeared to be pushing a little too hard. Williams did its usual 'Friday thing', while force India is also looking strong.
Toro Rosso, which had its drivers using different aero packages, will continue the programme for the rest of the weekend, Sainz using the new package and Kvyat the old.
Talking of updates, at Haas Romain Grosjean had a nightmare day, suffering an air intake issue in the first session and hitting the barriers in the second. The Frenchman blames the updates for his ills and said he wants to return to the old spec.
McLaren was another team with issues, Button and Alonso bookending the sessions by stopping on track. Despite the problems, the Woking outfit remains confident.
While only two drivers suffered damage to their cars yesterday, a number had very close encounters with the barriers, particularly at Turns 11, 18 and 22. Rosberg had his mishap at T18.
Air temperature is 31 degrees C, while the track temperature is 39 degrees. It is quite cloudy.
Because this session takes place in daylight, conditions are not really relevant to tomorrow's race, unlike qualifying later.
The lights go green and the Haas duo, headed by Grosjean, lead the way. In time they are followed by Ericsson and Vettel.
Button heads out on supers, as does Rosberg, while the Ferrari duo is on ultras and the rest on softs. A good mixture.
Much like FP1, most drivers complete an installation lap before returning to the pits. Only Wehrlein posts a time, though it is an unrepresentative 2:04.121.
Wehrlein does a Grosjean, in that he spins and clouts the barrier damaging his rear wing. Though he is able to continue the session is red flagged.
"I crashed," he admits to his team. As he is told to return to the pits bit of his rear wing fall from the car on to the track, hence the red flag.
Just before the red flag, Verstappen had posted a 47.038 and Massa a 48.579.
Replay catches Verstappen reporting: "There's a giant lizard on the track!" And sure enough there is a pretty bog big lizard running across the track in front of the Dutch driver's car. "You came face to face with Godzilla then," replies the team.
The session resumes, again Grosjean is first out, followed by Gutierrez, Raikkonen and Ocon.
Nasr makes a mistake as he passes Gutierrez. "It's all okay, just Gutierrez, I don't know what he is doing on the road!" moans the Brazilian, even though he appeared to be partly to blame. Indeed, there is a similar comment from the Mexican. "He does not know what he is was doing," he complains.
Another minor incident involving a Sauber driver as a very quick Sainz is blocked by a very slow Ericsson. Sadly, that's the problem with street tracks... that and giant lizards.
A 46.813 sees Raikkonen go quickest, but Rosberg subsequently posts 45.544.
"Big understeer, very big understeer, can we stop this lap," cries Button. "He is told to pit.
Hamilton goes second (45.806), demoting Vettel, like his teammate he is on the supers, whilst the Ferrari duo, in third and fourth, are on ultras. To further confuse the issue the Red Bull duo, in fifth and six, are on softs.
A 46.842 sees Sainz (ultras) go fifth, as Bottas gives the barriers a kiss.
As Vettel goes quickest in S1, but ultimately fails to improve, Hamilton takes to the escape road at T7. He heads back to the pits.
Verstappen gets massively out of shape, his rear end sweeping across the kerbs at T7. Drivers really do seem to be struggling for grip today, as Vettel confirms. "I think you've seen, I need a lot more rear on entry," says the German. "I'm a passenger!"
Sainz improves to fourth with a 46.279 as he continues with the updated aero package. Teammate Kvyat, with the old, is currently eighth (47.273).
"The pace of Red Bull on ultrasofts is going to be very interesting to watch," admits Pirelli. "A close fight on our hands."
Vettel is unhappy with his car and tells his crew what changes are needed, including going back to yesterday's settings. "The problem seems to be the rear of the car is too nervous," says the German. "I'm struggling to really get a feel for the tyres, especially the rears. It just doesn't seem to bite and grip up if you see what I mean. Any indication from the tyre guys is welcome." As the crew get to work he climbs from his car.
Check out our Saturday gallery from Singapore, here.
Toro Rosso's problem is further clouded when Kvyat improves to fifth, just behind his teammate, albeit 0.5s slower.
Perez (supers) improves to ninth (47.038), two spots behind his teammate.
The Saubers, Renaults and Manors all over 3.5s off the pace.
With 17:40 remaining, Rosberg heads out on the ultras. Followed by his teammate. The Mercedes duo have the track to themselves.
As was the case yesterday, Hamilton complains of heat in the right-hand side of his cockpit.
Rosberg is quickest in S1 and again in S2, while Hamilton subsequently goes quicker in the first sector. As Rosberg crosses the line at 44.352, Hamilton is stationary in the escape road at T7 after a massive lock-up. Not for the first time here, the Briton appears to be overdriving.
The Red Bull duo are now on track, both on the ultras.
Ricciardo can only manage PBs in the first two sectors, finally crossing the line at 44.903 to go second, 0.551s down on Rosberg.
Back in the garage, the Mercedes crew swarms over Hamilton's car.
Verstappen posts a PB in S1 but then goes quickest in S2. Elsewhere, Ricciardo reveals that he is enjoying Ocon's company. Verstappen crosses the line at 44.411, 0.059s down on Rosberg.
Raikkonen goes third with a 44.860, 0.508s down on the pace-setting Mercedes.
Despite the changes, Vettel can only manage PBs in all three sectors, crossing the line at 45.104 to go fifth.
"There's something wrong with the throttle pedal," complains Palmer, it's jumping." "Can you drive or do you need to box?" he is asked. "I can drive but I can't keep the car steady at low revs." He responds.
With just over five minutes remaining, Hamilton is back on track. Gutierrez is the only driver that hasn't tried the ultras in this session.
Perez improves to tenth (46.112), but is still some way off his teammate's pace.
While Alonso is 11th, Button is down in 16th, not the sort of pace McLaren was expecting. "Where does that put us?" asks Button, when told P16, he replies "wow!"
Sainz improves to ninth with a 45.879, two spots down on his teammate (45.503).
"This is the worst car I have driven for a very, very long time," reports Grosjean, not the sort of thing you want to hear from your driver.
Rosberg is quickest, ahead of Verstappen, Raikkonen, Ricciardo, Vettel, Hulkenberg, Kvyat, Hamilton, Sainz and Bottas.
Perez is eleventh, ahead of Alonso, Gutierrez, Massa, Magnussen, Button, Nasr, Grosjean, Ericsson, Palmer, Wehrlein and Ocon.
We began by saying that yesterday's sessions posed more questions than they answered, an hour later and in many ways we are none the wiser.
Check out our Saturday gallery from Singapore, here.