Lewis Hamilton conceded Mercedes had "obstacles" to overcome before leaving the first F1 pre-season test with a one-two at the top of the timesheet.
The seven-time champion put in a late flurry of fast laps on soft tyres to finish with the week's fastest time of one minute 19.138secs, just under a tenth of a second faster than new team-mate George Russell.
The week was not without issue, however, for the eight-time consecutive world constructors' champions.
Hamilton's tally of 94 laps on the final afternoon of running beat his combined total from the first two days by four of the Circuit de Barcelona-Catalunya.
"It has been an interesting few days," said Hamilton. "It has not been the easiest or most smooth running but definitely [we] had some obstacles to overcome.
"Of course, we always want more laps but I am happy with today. I think I got almost 100 laps in today so for a half-day of running, that is not too bad.
"The car is a lot different to previous years to drive, as are the tyres, but we are working our way through.
"We just need to download all of this data and get through it as much as we can next week and put one foot in front of the other."
Hamilton 'clueless' on Mercedes ranking
The track was wetted by tankers at the beginning of the final afternoon session in Spain in order for Pirelli to measure the performance of its new 18-inch wet and intermediate compounds.
The track dried throughout the four hours, with Hamilton setting laps in a more qualifying focused configuration in the late afternoon.
Asked how the car responded on low fuel, the British driver replied: "It was a damn sight better than earlier on when it was damp, when it was wet. It wasn't good at the start of the session with all that wet running.
"But the car was definitely feeling better with the fresher tyres and it is good to get a good feel for the different compounds."
On where he believes Mercedes sit in the pecking order, Hamilton insisted: "We have no idea where everyone is."