McLaren has opted to assign a fourth power unit to Lando Norris in Mexico City, a change that will send the Briton to the back of the grid on Sunday.
Norris is the second Mercedes driver to receive a new engine at the Autodromo Hermanos Rodriguez, with Aston Martin's Lance Stroll also the recipient of a new engine, while Honda-powered Yuki Tsunoda has also undergone an engine change.
So far, McLaren has enjoyed a rather low-key performance in Mexico City, so hopefully the engine change will perhaps boost the team's prospects.
On Friday, Daniel Ricciardo completed just a handful of laps in FP2 before he was sidelined by a gearbox issue, while Norris struggled with balance and grip issues.
The Briton was nevertheless hopeful of improving on Saturday.
"We can be confident we’re going to make some improvements into tomorrow and find a bit more lap time," said Norris at the end of Friday's running.
"It’s not easy, so we’ll work hard overnight and see what we can find."
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