Another race weekend means yet another grid penalty for Toro Rosso driver Pierre Gasly, who will start Sunday's Mexican Grand Prix from the back of the grid.
Honda confirmed on Friday morning that they were fitting a new, latest specification power unit into the back of the Frenchman's STR13 for this weekend's event.
Gasly also started the United States Grand Prix at the back last weekend, after the team fitted a new engine with “minor modifications” to both his car and that of team mate Brendon Hartley.
But Honda's technical director Toyoharu Tanabe confirmed that Gasly now needed a second new unit in seven days. He ascribed the move to "a concern regarding the assembly of the one used in Austin."
"That PU has been sent to Sakura for a full inspection," Tanabe continued. "At the moment, we are not sure if we can use it again this year.
"Therefore, by fitting a new one here, we add one to the pool of available units for the rest of this season.”
Having run the new unit in Friday morning practice at the Autódromo Hermanos Rodríguez, Honda will revert to an older specification of engine used earlier in the season for FP2.
“From FP2 and for the rest of the weekend, Gasly will run an older specification PU," Tanabe confirmed. "Brendon is also using this spec, for the entire weekend.
“The reason for reverting to the earlier pre-Russia spec is that we have a better understanding of this version of the PU and are more confident in our ability to set it up correctly for the specific conditions here in Mexico City.”
All teams are concerned about the power and reliability of their engines in the high altitude conditions of Mexico City.
Meanwhile, Hartley will be getting the chance to try out the aerodynamic updates that Toro Rosso introduced in Austin.
Wet practice meant that team didn't have enough track time last Friday to get the data required to run the upgrades in the race, so Hartley will pick up the baton with testing duties this time.
"Pierre wasn’t happy with the balance in FP3 when he ran the aero, so I think that’s partly why they removed it," explained Hartley.
"It’s going to be interesting to see how it performs," he added. "[We'll see] if we can get any more performance out of it. And then in terms of the rest of the weekend, I think there’s not a clear plan yet.
"There’s a lot for the engineers to look at, data-wise," he added.
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