Valtteri Bottas held a nine-tenth advantage over Mercedes teammate Lewis Hamilton as the two Silver Arrows sent a warning shot to their rivals in first practice at the Spanish GP.
The Finn set a 1m18.148s on the Soft compound tyre as he kept improving for the first hour of the 90-minute session. That time is already comfortably faster than last year's pole position time and is a result of the softer tyres and a new track surface in Barcelona that is offering much higher grip.
Bottas' world champion partner used the Medium compound for the second half of FP1, explaining the large margin between the two drivers, but Hamilton's initial best on his first set of Softs was still enough to remain P2.
Ferrari, with the new Halo-mounted mirrors as part of their upgrade package, seemingly took things easy with Sebastian Vettel in third and Kimi Raikkonen fifth despite using the Supersoft rubber to post their best times.
In between was the Red Bull of Max Verstappen, as the Dutchman produced a strong late effort on the Medium tyre to finish fourth.
Blustery conditions in Catalonia also made producing an error-free lap very difficult with a number of drivers spinning or running off at various points around the circuit.
The most notable victim was Daniel Ricciardo as the Australian locked his brake while dealing with a tailwind into Turn 4 and slid across the gravel before gently hitting the barriers but still causing sufficient damage to end his session after just 40 minutes.
He would still finish seventh in the final standings just behind home favourite Fernando Alonso in the new-look McLaren thanks to a radical new front nose design.
Romain Grosjean was another driver to have several excursions off track, including a near carbon copy of Ricciardo's off at Turn 4 but managed to avoid the barrier, despite his issues the Haas driver would be eighth fastest.
Stoffel Vandoorne added to McLaren's optimism in ninth with Pierre Gasly rounding out the top 10 for Toro Rosso.
Lap times were not the focus of many teams, however, as they completed aero testing of the new upgrades which every team traditionally brings to the first race in Continental Europe.
That will likely explain why neither Renault featured particularly strongly with Carlos Sainz only 15th and Nico Hulkenberg 17th, the two Force India's also lagged with Sergio Perez 13th and Esteban Ocon 16th.
Sauber did have a good morning, however, with Charles Leclerc in 12th and Marcus Ericsson 14th for the Swiss team.
Williams would bring up the field with Robert Kubica making his first practice appearance of the year and finishing 1.2 seconds clear of Lance Stroll, as the Canadian's session ended in the gravel at Turn 5, causing the second of two Virtual Safety Car periods.
