Although he stopped twice on track on Thursday, Nico Rosberg says the reliability of the W05 is better than Mercedes had expected.
The team covered the most miles of any outfit at the opening test in Jerez and continued to pile on the laps in Bahrain.
Behind the wheel of the W05 on the second day, Rosberg added a further 85 laps to the tally while his 1:36.965 put him fourth on the timesheets.
"It has been because we are better than expected with reliability," he said.
"Our own expectation was that it would be even more difficult, so from that point of view we are pleased as everyone has done a good job to make this car relatively reliable to start off with - reliable in a way that we can do a lot laps and start to see little problems and also start to work on performance.
"The first part of testing was about reliability and I think we did a decent job of that - getting a lot of laps done and understanding where our weaknesses are on the car and what we need to work on.
"Performance is obviously the most important and we don't really know where we are yet on performance, so that we will wait and see."
The 28-year-old, though, did run into a few problems on Thursday morning when he stopped out on track not once but twice.
Rosberg downplayed the issues conceding it is better to have them now than later.
"It depends because issues are issues and finding stuff on track is never good, but it is better to stop now as we at least get to see where the problems are.
"Of course there are going to be problems in the car, it is impossible that it would be perfect, so we need to push this car to the limit, we need to get to the problems and see them because that is the only way we are going to fix them for the races. So stopping on track isn't necessarily a bad thing."
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