McLaren wrapped up practice for the Austrian Grand Prix with Lando Norris leading Formula 1 leader Oscar Piastri in another one-two at the top of the timesheets ahead of Red Bull's Max Verstappen.
Norris, second overall and 22 points behind Piastri after 10 of the season's 24 races, lapped the Red Bull Ring with a best time of 1:04.324 and 0.118 quicker than the Australian.
Verstappen was 0.210 off the pace, with a big spin at the last corner at the end of the session, and was followed by Ferrari's Charles Leclerc and Lewis Hamilton in fourth and fifth.
McLaren have topped two of the three sessions, with Mercedes' George Russell fastest in the opening one on Friday but sixth on a much warmer Saturday and getting hotter.
"That's why it went a little bit belly-up for us. We were quite competitive until the end and then you can see really it goes above a certain threshold of temperature and we lose performance," Mercedes team boss Toto Wolff told Sky Sports television.
"The McLarens in high-speed [corners] is going to be very difficult to match.
"We changed the balance a bit yesterday and that was in a direction that wasn't so perfect. It came back more today but then the track temperature developed so drastically during the session, we went from 33 degrees to 42 and that makes a big difference."
Mercedes had Italian rookie Kimi Antonelli seventh, ahead of Aston Martin's Lance Stroll, Red Bull's Yuki Tsunoda and Sauber's Gabriel Bortoleto completing the top 10.
Norris was also fastest in Friday's second session and is looking determined after drawing a blank in Canada two weeks ago when he collided with Piastri.