Lewis returned to the cockpit of the W09 in the afternoon, quickly getting to work on race simulation work and data gathering on Pirelli's new tyre compounds.
The four-time World Champion leap-frogged team-mate Valtteri with a 1:19.296 in the final 30 minutes of the session, also setting his best time on the Mediums.
"Our week has been very productive so far," Lewis explained. "We got through everything we needed, reliability has been fantastic and the car feels great.
"We have not been working on balance, but in terms of some of the issues we had last year, a lot of them appear to have been removed. We get great correlation when we change bits of the car, so it's been a smooth transition this year so far.
"The track is very different to what it used to be because they resurfaced it. So it's difficult to know what all the experience means once we get to Melbourne. But, I definitely feel that we're moving in a positive direction. I'm really proud of everyone. They've been working so well in the team, the synergy is great at the moment.
"On another note, I know it's International Women's Day today so happy International Women's Day to all the ladies, to my Mum also and to my sisters. I think it's an amazing time for women. In my team, there's more women engineers than ever before. So I think it's a good time and I hope everyone has an amazing day."