The Mercedes engine is a significant factor behind Sainz's move.

      Carlos Sainz candidly recognizes that a significant factor in his decision to join Williams as his new Formula 1 team is the Mercedes engine. With a championship-winning power unit in the current era of regulations, Mercedes’ customer engine program has proven successful, highlighted by McLaren’s constructors’ championship win in 2024. As the regulations undergo substantial changes in 2026, Sainz expresses his hope that Mercedes will again excel at the start of this new regulatory phase next year.

      "I’d be lying if I didn’t say that one of the reasons for my move to Williams is the Mercedes engine in 2026," he told Soy Motor. "It’s part of the reasoning." He further mentioned, "I hope that in this respect, the Mercedes engine will contribute to the success and revitalization of Williams."

      After being overlooked by Red Bull and Mercedes’ main team, 30-year-old Sainz had to select from midfield teams for 2025 after his exit from Ferrari. "I can’t pinpoint the exact moment I decided on Williams, as it was a gradual process," he stated. "I convinced myself more and more as I asked questions and sought information from the various teams. Like with everything, I could be wrong or I could be right. Only time will reveal that."

      Sainz maintained a positive demeanor despite his situation last year, as Ferrari prepared to bring Lewis Hamilton on board for 2025, yet he admits it was a "very tough" time. "It was a challenging six months, having to perform on track while also deciding my future with teams positioned in the middle and back of the grid," he explained. "That surely impacted me somewhat during the season, and I had to manage both situations. However, I eventually convinced myself that Williams was the best option and the one I wanted the most."