Former McLaren driver Stoffel Vandoorne claims Red Bull are running with a completely different Honda engine to the one he knew.
The Belgian spent three seasons between 2016-18 with the Woking outfit during their engine partnership with Honda, including two full years in a race seat.
He was replaced at the end of 2018 after a poor campaign and joined the Formula E grid, while continuing as a simulator driver for Mercedes.
Now, Red Bull are armed with the Honda engine, and while Vandoorne claimed it is “definitely no longer the one he knew”, he also believes that it’s too early to say that Austrian team can challenge for the World Championship.
“We know that other teams are hiding their game, so we don’t know exactly,” he told Ziggo Sport.
“I think Red Bull, with the Honda engine, will have a chance to get involved in the fight for victory.
“It’s definitely no longer the Honda engine I knew from my time at McLaren.
“Whether they are able to join the fight for the title, it’s too early to say.”
Vandoorne also discussed his role with Mercedes, saying his simulator work wasn’t very fun, but vital for their relationship.
“It’s not the best fun, but it’s very important for me and my relationship with Mercedes,” he explained.
“I give information to the team and they give feedback to me about what needs to be improved on the car, and we then try those things in the simulator.
“It’s a different role for me, but it’s nice to have an influence on the car.
“The way they work is quite different from what I experienced at McLaren: how they prepare the car, how they prepare for the season, and the efforts they put in to succeed.”