Daniel Ricciardo gave Red Bull the ideal start to the 2018 season after topping the timesheets and the distance covered chart on the opening day of Formula 1 testing in Spain.

Using the medium compound tyres, the Australian set a very solid 1:20.179s moments before the lunch break and it would go unbeaten as he ended two-tenths clear of Valtteri Bottas, who also set his best time late in the morning.

Freezing temperatures and rain in the final hour restricted running in the afternoon, however, a number of laps in the wet meant the 28-year-old was the only driver to reach the 100-lap mark on Day 1.

The most notable incident on Monday was at McLaren, where Fernando Alonso spun into the gravel at the final corner on just his fifth lap after the right-rear wheel came off his MCL33.

Later, executive director Zak Brown revealed a wheelnut issue had caused the problem but it would cost the British team several hours and then because of the conditions couldn't meaningfully make up that time.

Kimi Raikkonen and Nico Hulkenberg had led the way for a prolonged period before the two late flyers from Ricciardo and Bottas, nevertheless, both remained within four-tenths of the leading pace in third and fourth respectively.

Hulkenberg's Renault team would go on to complete the second most laps of anyone on Monday with the German managing 72 in the morning and teammate Carlos Sainz 27 after the break, combining to just fall short of the century mark.

Toro Rosso was third on the lap count as Brendon Hartley managed 93 tours of the Circuit de Barcelona-Catalunya, which is a highly positive start for their new engine supplier Honda.

The usual marathon runners Mercedes and Ferrari had solid totals with Bottas and Lewis Hamilton combining for 83, three more than Raikkonen in the Prancing Horse.

On the timesheets, Alonso was fifth fastest for McLaren with compatriot Sainz in sixth. The world champion was seventh in his Silver Arrow, fractionally ahead of Hartley.

Williams had a steady start with Lance Stroll eighth and Sergey Sirotkin last in 13th, combining for 72 laps. Romain Grosjean was 10th for Haas, ahead of Marcus Ericsson's Sauber.

Force India development driver Nikita Mazepin caused the only other red flag after going off at Turn 4 in the morning, the Silverstone-based team would complete the least laps of anyone with just 22 as a result.