Lewis Hamilton described his first day of running in the 2012 McLaren as "all positive so far" - expressing his cautious satisfaction with the speed of the car and his relief that it was proving much more reliable than the 2011 model had at this stage.
McLaren has enjoyed a much smoother start to its winter than 12 months ago, when its car required a massive last-minute redesign after relentless reliability problems in testing.
Hamilton took over the MP4-27 from team-mate Jenson Button today and ended the session fourth quickest.
"I'm happy to be back and it was a day without any troubles and quite a few laps compared to last year. All positive so far," said Hamilton.
"I was a bit cautious going into today because looking at the times Jenson was experiencing over the last couple of days, I wasn't really sure where we were going to be.
"But when I got the new tyres on I was able to extract the grip quite easily and felt there was definitely something we could work with."
He warned that McLaren still had a long way to go to fine-tune the new car and claw back downforce lost to the ban on exhaust-blown diffusers.
"This car is definitely not predictable at the moment, being brand new. We haven't yet figured out the right set-up of the car," said Hamilton. "There are lots of different test items that we're going through.
"It feels like an evolution of last year's car but also there are some things that are not so good. The downforce on the rear for instance, is not as good through the high-speed corners as it was last year, but I'm sure we'll get that back.
"The car's better on the braking this year for some reason. Corner entry seems to be quite good."
Hamilton added that he expected last year's champion team Red Bull to remain strong based on its RB8's times so far, and reckoned Lotus's impressive pace this week was probably genuine.
"I think you can see the Red Bull looks quick. The Lotus looks quite impressive," he said.
"You never know what fuel loads people are on. I think we've been quite aggressive with our fuel loads."