Daniel Ricciardo says he doubts he can maintain his current supremacy over Mercedes across the remainder of the Monaco Grand Prix weekend, but is hopeful of staying in front, after topping Thursday's second practice session.
Ricciardo vaulted to the front of the pack with two rapid times, the second of which meant he ended the day 0.606s clear of Mercedes' Lewis Hamilton.
Ricciardo, chasing his first victory since 2014 and first pole position in the sport, is wary of Mercedes making gains on Saturday but hopes he can resist a fight back.
"The [upgraded] engine has helped a little bit but obviously we have a good car around here as well, I think it’s down to a little bit of both," he said of his pace.
"We are in a good position, depending on what the track is going to do on Sunday. I have good confidence with the car which is very important around here.
"Come qualifying and race day Mercedes will turn it up but hopefully I can stay in front. I’ll be surprised if we can keep the gap we have today in qualifying but we will see how we go.
"If the weather stays the same for the race and qualifying we won’t change too many things. The goal here is pole and win."
Team-mate Max Verstappen was fourth quickest in the sister RB12.
"There’s always a lot of work to do but I think it’s a good start," he said.
"It’s good to get back in the car and this track is very challenging so that’s always nice to do.
"On my short runs I had a bit of traffic and also when Sebastian [Vettel] spun I was behind him, but these things happen in practice and of course it was a great lap time by Daniel."