Budapest, Hungary - Robert Kubica completed 142 laps of the Hungarian Grand Prix circuit on Wednesday in a test that could lead to a Formula One race comeback more than six years after his career was cut short by a rally crash.
Kubica, who partially severed his right forearm in the horrific 2011 accident, was fourth fastest overall, 1.4 seconds slower than Ferrari's Formula One leader Sebastian Vettel.
He said, however, that he was "not 100 percent happy" with his day's work, which amounted to two Hungarian GP race distances.
"You can predict it wasn't easy, which I'm not hiding, but it was good," he told reporters. "I could drive I think tomorrow easily so the fitness level is good, which is a good sign.
"There are sides which need to be improved or need to get better but it's always like this - once you are here, you want to do better and more. But I have to say we have to be happy and I'm happy."
It was the first time Kubica, a race winner with BMW Sauber in 2008, had driven a 2017 race car and the two-day test was also his first time back in the paddock since his accident. He had always said he would only return as a driver and not as a guest.
Speculation about Kubica's return has gathered pace since he impressed the team in the 2012 Renault.
Team manager Cyril Abiteboul said in July: "He is still quick, he is still very consistent and more importantly he has this energy and this drive, this enthusiasm that he has always had"
Abiteboul added that Renault had "not seen any obvious roadblocks" to a possible comeback. The team looks likely to have a vacancy at the end of the season, and maybe sooner, with Britain's Jolyon Palmer struggling. He is one of just two drivers yet to score a point in 11 races this season and has been eclipsed by German team mate Nico Hulkenberg.
Vettel the pace-setter
Vettel, the race winner on Sunday at the Hungaroring, set the pace on Wednesday with British 17-year-old Lando Norris second on the timesheets For McLaren with 91 laps.
McLaren racing director Eric Boullier said: "His feedback with the engineers has been valuable and accurate, and he’s certainly an asset to our test driver line-up - not to mention a potential star of the future."
Italian Luca Ghiotto did the most laps of anybody on track, 161, on his test debut for Williams.