Vettel fastest as McLaren's problems continue

WATCH: F1 drivers take to the track for testing in Barcelona (5:00)

Check out the best of Tuesday's action from the second week of testing in Barcelona. (5:00)

MONTMELO, Spain -- Ferrari's Sebastian Vettel topped the opening day of the final pre-season test as McLaren lost more mileage to reliability issues.

Despite significantly warmer conditions than last week, the quickest times on Tuesday were over a second slower than the benchmark lap time set at the end of the first test by Lewis Hamilton. Vettel's best effort was set in the morning using the medium compound tyre and gave the Ferrari driver a 0.200s margin over Valtteri Bottas in the Mercedes using the soft compound.

"All in all I think a solid days with no issues, so we could get through our programme," Vettel said. "It was a bit tricky with partly very windy conditions out there but for sure much better conditions than last week."

Max Verstappen was a further 0.053s off in the Red Bull using the medium compound while Hamilton set the fourth fastest time after taking over Mercedes' driving duties in the afternoon. The world champion was using the soft tyres and set a time 0.412s off Vettel's best.

But with so much testing time lost to bad weather last week, mileage was the priority over lap times on Tuesday and Mercedes and Ferrari led the way with 177 laps and 171 laps respectively. McLaren, meanwhile, was dead last on just 38 laps after three reliability issues limited mileage throughout the day and caused two red flags.

Things started badly when Stoffel Vandoorne returned from his early-morning installation lap without power -- a problem McLaren later confirmed was an electrical shutdown of the power unit caused by the power unit's battery. After just over an hour in the pits, Vandoorne emerged on track once again only to complete two more laps before the Renault power unit -- and its telemetry being fed back to the pits -- cut out for a second time as he arrived on the pit straight. The car then remained in the garage until the final minutes of the morning session when Vandoorne returned to the track to complete three further laps.

In the afternoon the McLaren's lap tally rose to 38 before a hydraulic issue brought the MCL33 to a halt at Turn 3. It did not return to the track again for the rest of the day.

Out of McLaren's five test days this year, the car's running has been restricted by reliability issues on three and a further day was lost to poor weather last Wednesday. It means the team has just one clean test day under its belt since the start of testing and has just three days left to make up for lost time before the Australian Grand Prix later this month.

The two other Renault-powered teams completed more mileage with 139 laps for the works Renault car and 129 laps for the Red Bull. But later in the day Verstappen also caused a red flag when his Red Bull stopped at Turn 1 with a battery problem after exiting the pits.

"Those problems could have affected any of the three teams, so of course it's an issue for us," Renault technical director Bob Bell said. "But the reason we do this testing of those components before going to Melbourne is to find the ones that have got problems, so that when we go to Melbourne we have a stock of batteries that we are completely confident in. It's the right thing to do, we have found some that are not fit for purpose and that's great."

Asked if the issues could be due to the McLaren or Red Bull design, he added: "The issues that we've had I don't think have any relation to the installation of the battery."

Elsewhere, the Honda-powered Toro Rosso had a brake issue after 54 laps in the morning and failed to make it out on track in the afternoon. The problem meant a planned driver swap from Pierre Gasly to Brendon Hartley in the afternoon did not go ahead. Gasly still finished fifth in the standings at the end of the day.

Kevin Magnussen was sixth fastest for Haas ahead of Nico Hulkenberg's morning time in the Renault and Carlos Sainz's afternoon time. Sergey Sirotkin was ninth in the Williams ahead of Sergio Perez in the Force India, Marcus Ericsson in the Sauber and Vandoorne's time in the McLaren. Lance Stroll finished the session at the bottom of the time sheets after completing 86 laps in Williams in the afternoon.

Times at close

1. Vettel, Ferrari, 1:20.396, 171 laps (Medium)
2. Bottas, Mercedes, 1:20.596, 86 laps (Soft)
3. Verstappen, Red Bull, 1:20.649,130 laps (Medium)
4. Hamilton, Mercedes, 1:20.808, 91 laps (Soft)
5. Gasly, Toro Rosso, 1:20.973, 54 laps (Soft)
6. Magnussen, Haas, 1:21.298, 96 laps (Soft)
7. Hulkenberg, Renault, 1:21.432, 48 laps (Medium)
8. Sainz, Renault, 1:21.455, 91 laps (Soft)
9. Sirotkin, Williams, 1:21.588, 42 laps (Soft)
10. Perez, Force India, 1:21.643, 93 laps (Soft)
11. Ericsson, Sauber, 1:21.706, 120 laps (Super-soft)
12. Vandoorne, McLaren, 1:21.946, 38 laps (Super-soft)
13. Stroll, Williams, 1:22.937, 86 laps (Soft)