Mercedes endured a frustrating start to the second week of Formula One testing in Barcelona, with Valtteri Bottas suffering an oil pressure problem.
The five-time defending constructors' champions are putting some new aerodynamic changes through their paces this week, notably a revised nose and front wing.
Lewis Hamilton was able to complete 83 laps in the first session on Tuesday, but Bottas' track time was limited around the Circuit de Catalunya.
The Finnish driver was forced to pull over soon after leaving the pits and although Mercedes worked hard to get him back out again, Bottas finished the day with seven laps to his name.
UPDATE: @ValtteriBottas stopped on track with an oil pressure problem.After initial investigation, we have decided to swap the PU in order to continue today's programme and also to pursue our analysis of the problem. #F1Testing pic.twitter.com/9toEMP9HfT— Mercedes-AMG F1 (@MercedesAMGF1) February 26, 2019
While Mercedes had to deal with uncharacteristic reliability issues, both Ferrari and Red Bull were far more productive.
Pierre Gasly topped the timesheets for much of the day for Red Bull, the Frenchman lapping two tenths faster than Ferrari's Sebastian Vettel in the second session.
Lance Stroll also impressed for Racing Point, but it was McLaren's Lando Norris who ended the day on top as he clocked a best time of one minute, 17.709 seconds.
Earlier on Tuesday, Antonio Giovinazzi set the pace for Alfa Romeo, the former Ferrari test driver deposing Gasly late on.
"We should not get too excited... everybody is hiding," Gasly told Sky Sports F1. "We just try to focus on ourselves and go through the programme we have, and so far, it's been good. We managed to do all the plan, a lot of laps, which is good for the engine and also the car.
"We know we have some good potential, but we don't know what the others are doing at the moment. We just try to improve in the areas where we think we struggle a bit. I think we have a rough idea. We just need to keep our head down and work. It's going to be tight.
"We're just trying to push a bit more day after day. But still we haven't pushed flat out."Published 27 Feb 2019, 00:13 IST