Fernando Alonso topped the timesheet of the one-day 'young driver' test after completing 105 laps of the Abu Dhabi Grand Prix circuit.
Alonso, who will return to Formula 1 with the Renault-rebranded Alpine team in 2021, stepped up his preparations with a full day of running in the 2020 car after previously only being able to test two-year-old machinery.
The 39-year-old was contentiously given special dispensation by the FIA to take part despite his two-time champion experience.
Previously, drivers who have competed in no more than two grands prix are permitted entry, but the FIA tweaked its own regulations to allow drivers who were not involved in this year's championship.
With a time of one minute 36.333 seconds, Alonso topped the order by 0.262s to Mercedes' Nyck de Vries.
The Spaniard's time was faster than those set by this season's Renault drivers Esteban Ocon and Daniel Ricciardo in qualifying at the weekend, pipping his future French team-mate by 0.026s.
Mercedes ran Formula E drivers Stoffel Vandoorne and de Vries in its two W11 cars, with the Belgian out in front in the pre-lunch session with a lap of 1:37.206s, finishing almost three-tenths of a second clear of Alonso.
Post-lunch, Vandoorne dropped behind de Vries but, other than Alonso, they were the only two drivers to set sub-97-second times.
Robert Kubica ended the day fourth for Alfa Romeo with Yuki Tsunoda, expected to be announced as a 2021 AlphaTauri driver in the coming days, fifth for the Honda-powered team.
Jüri Vips completed 101 laps for Red Bull in seventh. Former F1 driver Sebastien Buemi struggled to match the Estonian's pace and ended the day 12th of the 15 runners after making contact with a wall early in the day.
Callum Ilott, partnering Kubica at Alfa Romeo was eighth, 1.5s off the pace, with his F2 rival Robert Shwartzman 11th for Ferrari. The 21-year-old Russian completed a staggering 129 laps, more than two grands prix.
Mick Schumacher, fresh from being crowned F2 champion and landing a drive with Haas, was slowest on Tuesday.
The team has confirmed, however, it used the session to build up his procedural knowledge and was not focused on setting a headline time across his 126 laps.
GPFans is a multi-platform, multi-language brand dedicated to Formula One coverage. We bring you all the ins and outs of the sport, 24/7, everything from up-to-the-minute news and features to the latest viral stories and clips.
We believe that a new generation of exciting, outspoken drivers will make F1 more popular than ever before, and we want to give our users access to as much of their heroes as possible, on and off the track. From Lewis Hamilton to Max Verstappen, Daniel Ricciardo to Sebastian Vettel, we provide in-depth analysis of every every Grand Prix in the season, from Australia to Abu Dhabi.
With Formula One under the new ownership of Liberty Media, how the sport is being covered is evolving, and GPFans will look to be at the heart of this progression into new media, as one of the fastest-growing sites covering the king of motorsports.