George Russell declared Mercedes' new Formula One car nicer to drive than last year's tricky offering after racking up 122 laps of Bahrain's Sakhir circuit on the opening day of testing on Wednesday.

The Briton, who hands over to seven times world champion team mate Lewis Hamilton for Thursday's session, said it had been a positive debut for the W15 car.

The day's work included a full race simulation in the afternoon.

"From hitting the ground it felt like we had a good foundation to start from," said Russell, who ended the day 12th overall.

"We completed lots of laps and have plenty of data to go through tonight. We ended the day in a reasonably good spot and we can build from here over the next two days."

Russell, whose November 2022 victory in Brazil remains the former champions' last race win, said the focus will be on maximising mileage.

"Overall the W15 does feel nicer to drive than last year's car," he added.

"We know that it's not about the feeling, but the speed. Nevertheless, today was about learning and not about chasing performance.

"We're focused on ourselves at this test and it will only be next week where we see where we stack up against the others."

Mercedes, who are losing Hamilton to Ferrari at the end of the season, finished second overall behind runaway champions Red Bull last year but failed to win a race for the first time in 12 years.

Technical director James Allison said at the car's launch that last year's weaknesses had been addressed with a big effort to improve the 'spiteful' rear axle and providing more reassurance for the drivers.

The season starts in Bahrain on March 2. REUTERS