Mercedes is confident the revised aerodynamic package it debuted during the second Formula 1 pre-season test is an “improvement”, despite facing a disrupted day of running.

The reigning world champions brought a major bodywork update to the start of the second week of winter testing in Barcelona, as Lewis Hamilton emerged from the garage on Tuesday in a new-look Mercedes W10 sporting a host of new aerodynamic elements, including a bulbous nose and front wing, and revisions to the floor, side pods and endplates.

Mercedes delayed the initial introduction of the package it intends to use at the season-opening Australian Grand Prix next month in order to capitalise on enhanced development time, with five-time world champion Lewis Hamilton reporting an instant “good step”.

“We got through our run programme and the car was feeling relatively good,” Hamilton said.

“It was an improvement from last week which is a good step. The tyres are also working a better now that the track temperature is a bit higher.

“We have to continue to analyse everything and keep pushing.”

Valtteri Bottas’ afternoon running was truncated due to an oil pressure issue that caused him to stop on-track on his out lap following the lunch break.

After Mercedes completed a power unit swap, the Finn was able to rejoin the action for the closing stages of the session as he completed just seven laps.

“Unfortunately, after four days of flawless reliability last week, I spent most of the day waiting as we had an oil pressure issue on my first outlap and had to change the power unit,” Bottas said.

“But I'm glad I still got to do a few laps, the team did a really good job to get the car out again; it was important to get a bit of a feel for the new aero package.

“My running was obviously very limited, but it seems like we've made improvements. We need to review everything in more detail tonight and I'm looking forward to continuing our programme tomorrow morning.”

Mercedes had originally sent Bottas out with some old-spec elements from its previous aero package to complete a comprehensive back-to-back analysis, although his early problems curtailed that plan.

“It was not exactly the day we hoped for, running for the first time with the bodywork kit that we expect to use in Melbourne, with a large part of the day lost to an oil pressure issue at lunchtime,” technical director James Allison explained.

“Nevertheless, either side of that problem we did do some useful things, finding that the car behaves a little differently with the new package.

“We're looking forward very much to have a trouble-free day tomorrow to get a better feel for what it can do.”