A notification from F1 technical delegate Jo Bauer after the opening free practice session said that the fuel that Hamilton planned to use was cooler than is allowed under the rules.
The notification said: “The temperature of the fuel intended for immediate use in car number 44, measured at 17:44 with FIA approved and sealed sensor, was more than eleven degrees centigrade (20.3 °C) below the ambient temperature recorded by the FIA appointed weather service provider one hour before the first free practice session (32 °C), this not being in compliance with Article 6.5.2 of the 2019 Formula One Technical Regulations.
“I am referring this matter to the stewards for their consideration.”
Cooler fuel delivers a performance benefit in terms of power and density, and the FIA has long had a limit of how low the fuel can be taken in a bid to try to stop teams taking things to extremes.
The issue is unlikely to result in a competitive sanction for Hamilton nor Mercedes, with Alfa Romeo being fined 5000 Euro for a similar offence in Austria this year after the fuel intended to be put in Antonio Giovinazzi’s car was found to be too cold.