George Russell and Kimi Antonelli will face Sepang’s extreme heat without wearing Formula 1’s cooling vest after Mercedes chose to prioritise resources for development of the W17. George Russell already knows what awaits him in Malaysia, describing the experience as being “like sitting in an oven”, but the team decided that investing further in the driver-cooling equipment would come at the expense of car performance.
The decision reflects another compromise created by Formula 1’s cost limits. Mercedes had to choose where to allocate its resources, and development of the Mercedes W17 took priority over making the cooling vest sufficiently robust for race use.
Why George Russell and Kimi Antonelli will not use cooling vests at Sepang
Neither Kimi Antonelli nor George Russell will wear the cooling vest in Malaysia. The equipment can provide drivers with some relief from the intense heat generated both by the ambient conditions and by the car itself.
Because wearing the vest is not mandatory under the regulations, Mercedes chose not to devote additional resources to developing the equipment when those same funds could instead be used to improve performance and reliability.
How the Formula 1 cooling vest works
The cooling vest resembles a conventional vest, but it is not simply cooled with ice. It forms part of the Driver Cooling System, which is integrated directly into the car.
Under the 2026 Formula 1 technical regulations, when a Heat Hazard is active, the system must be capable of extracting at least 200 watts of heat from the driver at an ambient temperature of 40°C.
That requirement means the cooling equipment is not merely an accessory that can be added to a car when required. It needs to be integrated into the vehicle’s infrastructure, including the associated pump, pipes and other components, while also operating correctly and continuously during the race.
All of that carries a development and operational cost. Mercedes therefore chose to reduce spending in this area so that resources could remain available for the evolution of the car.
What the FIA Heat Hazard rules require
The Heat Hazard protocol was introduced by the FIA to protect drivers when extreme temperatures are expected. It can be activated when the official weather service predicts a heat index above 31°C during a Sprint or Grand Prix.
Once declared, the Heat Hazard remains in force for the event. The car must then be equipped with the required Driver Cooling System components, including the pump and pipework.
The driver, however, is not obliged to wear the personal cooling equipment itself. If a driver chooses not to use the vest, the applicable mass requirements ensure that the car does not gain an advantage simply by running lighter than one whose driver is using the system.
Mercedes chose W17 performance over cooling-vest development
Mercedes brought another package of updates to Sepang for the W17, including modifications to the floor and other areas of the car. Those developments increased expenditure and made it necessary to save resources in areas the team did not regard as essential for improving outright performance or mechanical reliability.
“We won’t be using the cooling vest because we haven’t invested the resources required to make it robust enough,” George Russell admitted.
“But the team pointed out to me: look, we can develop it and we can invest the money required… but at the expense of performance.”
The decision illustrates the trade-offs Mercedes continues to make as it develops the car while fighting at the front of the championship. The latest Mercedes developments have remained focused on extracting more from the W17 rather than diverting resources into additional cooling equipment.
Sepang conditions put drivers under severe physical strain
The conditions at the Malaysian circuit have already been extreme. During the opening day of practice, air temperature exceeded 33°C while the asphalt reached 60°C, accompanied by high humidity.
Against that backdrop, George Russell and Kimi Antonelli face a demanding physical challenge. Mercedes nevertheless had little doubt about its priorities when choosing between greater driver cooling and the opportunity to make the car faster and more reliable.
The severe Malaysian conditions are expected to remain one of the defining factors of the weekend, with the full 2026 Bahrain Grand Prix at Sepang schedule and circuit guide providing the remaining session times and key circuit information.
