Mercedes dominated the first day of Formula One preseason testing on Monday, sending a message that the overhaul of regulations may not derail the three-time defending champions.
While Lewis Hamliton aimed for speed, new teammate Valtteri Bottas went for distance as they shared timebehind the wheel of the revamped Silver Arrow.
Hamilton took over driving in the afternoon and clocked the day's fastest lap, bettering Sebastian Vettel in his Ferrari by 0.113 seconds.
In four hours of driving before lunch, Bottas outworked the rest of the field with 79 laps at the Circuit de Barcelona-Catalunya. That total surpassed the 66 laps of the Spanish Grand Prix at the same venue.
Only Vettel and Felipe Massa ended up with more laps, but that was in double the time following the entire eight-hour session.
Australia's Daniel Ricciardo managed just four laps in his Red Bull when it came to a sudden stop and he and the car were left to go back to the pits.
"It's a great feeling," Bottas said after his maiden run in the Mercedes.
"(The engineers) did an amazing job in the winter. I only started a month ago, but what I have seen has been very impressive. For us, the main thing is to get the mileage now."
Mercedes' rivals are hoping the regulation changes will help them make up ground on a team that has won 51 of the last 59 races.
Other than Vettel's positive showing, there was little sign that the gap had closed.
Fernando Alonso joined Ricciardo as a driver left with frustrations. The McLaren ace was also stuck in the garage for hours following a sole trip around the track as its technicians repaired an oil-related problem with its Honda motor.
F1's rule changes to produce more downforce and grip by mandating wider vehicles and tires appears to have led to the desired result of boosting speeds.
To compare with times on the same track from last year, Hamilton's fastest effort of 1 minute, 21.765 seconds knocked a second off the fastest lap through a full eight days of testing in 2016. It was also faster than Hamilton's pole- winning lap of 1:22.000 at the Spanish GP.
