Red Bull chief technical officer Adrian Newey believes Honda's enthusiasm has been completely different to Renault's in Formula 1's turbo-hybrid era.
Renault and Red Bull parted ways at the end of 2018 a their relationship deterred due to a mixture of poor results and engine failures. Newey has revealed Red Bull thought it would be nearly impossible to win a championship with Renault after 2014.
"With Renault during the V8 era, we had a very close and tight relationship with them," said Newey on Talking Bull. "I felt we were treated completely equally with the works team.
"Whereas as the hybrid era rolled on, then the relationship between Renault and ourselves became increasingly difficult and fractured. So it became a difficult period where we in truth knew that it is always going to be near impossible to put up a championship challenge because we will be too far back."
Red Bull partnered up with Honda in 2019 and are currently mounting their first serious title challenge for the first time in eight years. Newey says having Honda become Red Bull's engine supplier "gave everybody a new boost of energy".
"With Honda their level of commitment and enthusiasm and progress, then that's completely different," added Newey. "I think that level of commitment is such an important thing, it's not just the performance.
"If you can see that your partner is every bit as passionate and pushing just as hard as you are then, then you can kind of push each other along. And if one makes mistakes, then you can allow for that, you can't criticise them for doing everything they can."