The Pole, whose only F1 triumph came nearly a decade ago in 2008, drove a Lotus E20 painted in Renault's modern livery, completing 115 laps in total.
It was his first taste of F1 machinery since his severe rallying crash ahead of what was set to be his second season with the Lotus-Renault squad in 2011.
"I would like to thank everybody for making this possible, I hope it was a good day for everyone and maybe they saw something of my old, 2010 self," Kubica reflected.
"For me, it has been an important day from an emotional point of view. It has been a long time away from the paddock and I have been through difficult periods, I kept working hard and a few years ago I felt it was impossible.
"I have mixed feelings, I am proud with what I achieved today, but also it shows what I have lost.
"I don’t know what the future will bring, but I know one thing, after working for more than one year to prepare for this, I ran with good pace and consistent in difficult conditions.
"It is not easy after six years, but I knew I could do the job and I can be satisfied. I appreciate the opportunity. Renault gave me my first F1 test in 2005, so I appreciate another test this time around."
Renault's sporting director Alan Permane said the test was like turning back the clock, adding: "It was good to see Robert back in a Formula 1 car. [He] has changed a little, he is more mellow and he wasn’t as pushy when asking for every detail about the set-up of the car!
"His comments and feedback, however, were like turning the clock back for all of us. It is a tricky thing to jump into an F1 car after six years and it was a great performance from him.
"This was a one-off event for Robert. His time with Renault was cut short so abruptly and we perceived such a nice future with him. The team was in Valencia testing with Sergey Sirotkin, so it was the perfect opportunity to offer Robert a day in the car and contribute in our way to his recovery."