Mercedes has revealed that it had to turn down the performance of its engines during Friday practice at the Mexican Grand Prix due to overheating concerns.
Lewis Hamilton and Valtteri Bottas finished the second practice session in seventh and ninth, with deficits of over 1.3s to the pace-setting Red Bulls. The gap to title rivals Ferrari was smaller at just 0.1s, but technical director James Allison is hopeful the team will be able to turn up the performance if the forecast for cooler temperatures over the weekend holds true.
"This is an unusual track, which places unusual demands on the chassis, power unit, cooling systems and tyres," Allison said. "From all our running today, we have to conclude that we have not yet found the best way to meet those unusual demands with good performance on both single laps and in the long runs.
"We were overheating the power unit in a number of areas today, and that meant we had to protect against this by turning it down as a precaution. With a bit luck, and no little hard work, we can get ourselves into better shape tomorrow and on Sunday, when conditions are also forecast to be cooler.
"We have plenty of work ahead of us overnight and in FP3 tomorrow to put ourselves in a stronger position than we were able to achieve today."
However, Hamilton, who can win the title this weekend as long as he finishes seventh or higher, believes the Red Bulls could be out of reach in Mexico.
"The car was good in some places, but not so good in others," he said. "It's not about one particular area; there are lots of different things that we can improve. It was difficult with the high track temperatures, which were melting and graining the tyres, but a lot of people were experiencing that today.
"Red Bull seem out of our reach at the moment, Ferrari are right there with us, but we're here to try and compete, so we will do the best we can to have a real race."