Pastor Maldonado ended the Barcelona test with the quickest time as Lotus seemingly shedded its troubles that plagued the team during the pre-season and the opening four races of the championship.
"That was a complete day for us and my first normal day of testing this season," said Maldonado, whose fastest time came on the supersoft tyres.
"We completed everything we wanted to do. We learnt a lot more about the car, the set-up and performance is improving all the time so I’m feeling more comfortable to push too. It’s been a big step forward," he reckoned.
The Venezuelan managed a trouble-free 102 laps at the Catalunya circuit and was nearly a second ahead of Mercedes' Nico Rosberg, whose programme began with a trial run of the 'megaphone' exhaust tailpipe as requested by the FIA.
"Everyone was talking about the exhaust but to be honest I didn't notice much difference in the sound," Rosberg said. "Of course, we're happy to try these things if that's what the FIA and the fans want us to do. But perhaps this was not the right solution."
Rosberg also focused on practice starts, as the German had admitted that his weak starts in the last three races contributed to teammate Lewis Hamilton upstaging him.
"It's not easy as it's such a sophisticated procedure and there are some highly complex parts involved like the clutch, for example. But we definitely learned some interesting things," he pointed out.
Ferrari made up for its lack of adequate mileage on the opening day by racking up 94 productive laps with Kimi Raikkonen, who set the third quickest time.
Esteban Gutierrez lost about an hour due to a power train issue but was fourth in the Sauber ahead of Williams' Susie Wolff and Jules Bianchi in the Marussia.
Defending world champion Sebastian Vettel had a late start due to overnight work solving the gearbox issues that halted Red Bull's running on the opening day on Tuesday. The German, though, managed 72 laps and posted the seventh quickest time.
Force India driver Daniel Juncadella was eighth and McLaren's Stoffel Vandoorne was ninth as both teams tested the 2015 tyres, as scheduled for Pirelli and provided for in the sporting regulations.
Vandoorne in his first running in a Formula One car managed a mammoth 136 laps – more than any other driver - completing more than 600 kilometres. As a result, the Belgian accrued enough mileage to earn himself an F1 superlicence.
In contrast, Daniil Kvyat did the least number of laps as the Russian performed aero tests for Toro Rosso, including straight line constant speed running, so did plenty of 'in' and 'out' laps.
"These tests involved making lengthy changes to the car, which meant not many laps were completed, although the results achieved were positive and will provide useful data for the upcoming races," the team explained in a statement.
Caterham was forced out of running, scheduled with Robin Frijns, after assessing the damage to the chassis following Kamui Kobayashi's crash late on the opening day.