The Briton took over the Mercedes car for the afternoon session after rookie team-mate Kimi Antonelli completed the morning programme. Russell went on to complete 95 laps, helping the Brackley-based team rack up more than 700 kilometres on day one of testing.
It marked the first major on-track running of the season, with teams allowed three days of testing this week. Seven teams were in action on the opening day as the sport began a fresh chapter shaped by significant changes to the power units.
Russell said it did not take long to feel the impact of the new technology.
“It’s amazing just to be back out driving again,” he said. “At the end of the year everyone looks forward to a break, but after a week or two you’re raring to go.
“There was a lot of anticipation around these new power units and, so far, the amount of power they give is pretty impressive.”
From the cockpit, Russell felt the cars were faster than ever around the Circuit de Barcelona-Catalunya.
“I think it’s probably the quickest I’ve ever seen an F1 car pass here,” he explained. “You can also feel the cars being smaller and lighter compared to previous years, which is a positive step.”
The day also saw new names on the timing screens, with Cadillac and Audi joining the action, while Red Bull ran its first in-house-built power unit.
Pre-season fears of major reliability problems, similar to those seen in 2014, quickly eased. Russell admitted he had been impressed by how smoothly rivals ran.
“I was pretty impressed with a number of other teams,” he said. “The Red Bull-powered teams had a really smooth day, Audi put in some good laps, and Haas did the most laps with a Ferrari engine.
“It’s not 2014 vibes at all. Formula One has evolved so much, and to see so many laps completed on day one was impressive across the board.”
For Russell and Mercedes, it was a confident first step into a new Formula One era.
