Felipe Massa says his Williams team's reliability has been a major boost during Formula One pre-season testing so far.
The Grove-team has managed nearly 800 laps over nine days of testing, with Massa covering 103 on his way to the fastest time of the winter so far at Barcelona on Thursday.
"It was a very, very good day, not only because we are in front, but because the car never shows any problems," said Massa, who has one more day of testing on Saturday before the first race of the season.
"We've never had any problems, so I think it's very important at this time.
"We cannot forget Mercedes is there and it's really strong, but I think we are doing our work in the best way we can and the team is very motivated and everything is going in a good line for them as well.
"We are there."
The Brazilian admitted, however, that Williams still needed to improve the consistency of its laptimes, although he concedes it is impossible to judge how strong it is compared to its rivals.
"When I needed to do the laptime, the laptime was good, but the consistency is something we are still working a lot to improve. I'm pretty happy but it's still too early.
"When everybody is on the same tyres, on the same fuel, at the same time is when we are sure where we are."