The Spanish GP could have looked very different for Red Bull had it not been able to rectify the fuel temperatures in Max Verstappen's car before the race. According to the regulations, the fuel temperature rules before the Spanish GP stated that the temperature needed to be at 18°C as soon as the cars took to the track. From the Spanish GP onwards, however, this was changed and the fuel was supposed to be 10°C cooler than the ambient temperature at the track.
Due to a change in rules regarding fuel temperatures, Red Bull almost ended up having its reigning champion start from the pit lane. With the track temperature at 35°C, the fuel temperature needed to be at 25°C, but the team kept the temperature at 18°C in compliance with the old rule. According to Article 6 of the FIA technical regulations:
“No fuel intended for immediate use in a car may be more than ten degrees centigrade below ambient temperature. When assessing compliance, the ambient temperature will be that recorded by the FIA appointed weather service provider one hour before any practice session or two hours before the race. This information will also be displayed on the timing monitors. The temperature of fuel intended for use in a car must be measured via an FIA approved and sealed sensor.”
As a last-minute measure to rectify the problem, Red Bull turned on the engine to heat the fuel to the required temperature.
Speaking to the media afterward, the Austrian team's advisor Helmut Marko admitted that the team had been in a fix just before the race and had to resort to running the engine to warm up the fuel. He said:
“We had overlooked that the temperatures had changed. However, we noticed it in time and ran the engine to warm up the fuel.”
Ferrari's team principal Mattia Binotto, however, raised an eyebrow when this was brought to his attention. While he did ultimately back the FIA decision on Red Bull's fuel temperatures, he admitted he was "curious" about what had happened and would give it a second look. He said:
“I can only rely on the FIA, so it’s hard for me to understand that Red Bull might have been heating up the fuel. That wouldn’t explain it because as I said, in my view, it should be at the right temperature at all times. Anyway, I can only trust the FIA and they have checked it and are apparently happy with it. I am curious about this matter.”
Red Bull was destined for a pit lane start if hadn't complied with the rule
Red Bull was destined for a pit lane start if it was found that the car's fuel temperatures did not comply with the regulations. Both the Aston Martin drivers suffered a similar fate in the Miami GP when it was found that the cars did not have fuel at the right temperature and both Sebastian Vettel and Lance Stroll ended up starting the race from the pit lane.