The team completed just short of two race distances, with a total of 104 laps (Nico: 59, Lewis: 45).
Nico Rosberg and Lewis Hamilton completed the first two practice sessions for the Bahrain Grand Prix in Sakhir today.
Nico Rosberg ( F1 W04 / 03 - 22 laps / 1:34.621 / P3 - 37 laps / 1:34.666 / P8): "Our test programme was pretty good today in that we managed to complete everything on our plan.
The car had a lot of understeer and the race will be very tough on the rear tyres. The problem is that when you want to save the rear tyres, you try to set up the car with more understeer and that costs you time over one lap.
So it's all about finding the right compromise. We've still got some work to do tonight to find a good balance for tomorrow and the race."
Lewis Hamilton ( F1 W04 / 04 - 16 laps / 1:35.792 / P13 - 29 laps / 1:34.976 / P10): "We worked as hard as we could today but couldn't quite get the balance of the car to where it needs to be.
I had some issues in P1 which we were able to improve for this afternoon so that's a positive, but we need to identify where we are losing time and find more performance.
We have changed the set-up of the car to what we thought would suit this track but we need to look at that and make sure it is the right direction to go.
The heat here is so hard on the tyres so another positive is that we did as many laps as possible to look at long runs and race preparation.
We're not as far off as we might look today but there is a lot of hard work ahead and it will be a tough battle for us this weekend."
Ross Brawn: "Neither driver enjoyed the same good balance today that we achieved during practice at the past three races and, in the hot conditions, that proved quite damaging for the tyre condition and therefore overall pace.
We got a good read on how the two tyre types compare and were also able to compare some set-up items such as downforce levels to assess their impact over long and short runs.
There is a lot of data to analyse and clear areas for improvement, so we will be working late into the night in order to find better solutions for tomorrow."
Toto Wolff: "It was no secret that we would be facing extremely hot conditions here in Bahrain and that they would make life pretty tricky if you had a car that was not well-balanced. We haven't yet found the sweet spot of the set-up and that was reflected in the timesheets today.
We need to find out why we seem not to be as competitive as we were in the past three races and get the right answers to take a step forward tomorrow relative to our rivals."
Mercedes AMG Petronas