Valtteri Bottas led Lewis Hamilton to a Mercedes one-two in second practice at the Abu Dhabi Grand Prix.
Bottas was 0.310 seconds ahead of Hamilton, who was 0.076secs faster than Ferrari's Charles Leclerc as the season's final race weekend began.
In an unusual crash for a practice session, Bottas and Haas' Romain Grosjean collided at a chicane.
The Finn dived for the inside at the end of the second long straight and Grosjean turned in having not seen him.
Both cars suffered extensive damage and showered the circuit with debris, causing the session to be stopped for seven minutes while the track was cleared.
Bottas and Grosjean were called to the stewards after the session, and the Mercedes driver was given a reprimand for his actions.
Until his crash, Bottas was on excellent form around Yas Marina on Friday, fastest in both sessions, but he has a grid penalty for excessive engine usage and will start the race from the back of the grid.
Hamilton, Leclerc and the second Ferrari of Sebastian Vettel were covered by just 0.125secs, with Red Bull's Max Verstappen fifth and 0.435secs off Bottas' pace but nearly half a second ahead of his team-mate Alexander Albon.
In an unusual feature, the Ferrari drivers' times were set on a second timed lap, the team choosing to run two sets of soft tyres on low fuel rather than the usual one.
And Leclerc's time came following a heavy brush with the barriers on his first run at Turn 19, where team-mate Vettel crashed in the first session.
Alfa Romeo's Antonio Giovinazzi also came to grief at Turn 19, although he managed to spin while avoiding hitting anything.
Mercedes ended the session emphasising their strength with some impressive pace on the race-simulation runs, with Hamilton comfortably quicker than Verstappen and Leclerc when running the soft tyre with a heavy fuel load.
"It's been a bit of an unusual Friday for me," said Hamilton. "I was struggling to get into the rhythm, but you have your good and bad days.
"I've been trying to explore some new avenues with the car. We already know where it works well, so I'm pushing the car into different places, just trying to see if there's anywhere else I can exploit the car and the tyres for the future."
Bottas said: "It's been a good day out on track; the car was well-balanced from the get-go.
"The end of my FP2 session was compromised by a minor incident with Grosjean; I thought he had seen me going for the overtake on the inside, but by the time I realised that he hadn't seen me, there was no way for me to escape anymore."
Vettel said: "We are pretty much fighting the same things as the last couple of races, so all these medium- and low-speed type of corners we are lacking speed compared to the others. Sector three is where it really hurts us."