Lewis Hamilton said he made the call to "sacrifice" his driving time during Tuesday's test at the Circuit de Catalunya after opting not to take up his scheduled track time in the afternoon.
Bitterly cold conditions meant drivers were unable to get sufficient heat in their tyres during the early morning running and Mercedes opted to limit Valtteri Bottas to a handful of installation laps in the opening hours. Ahead of the lunch break the sun warmed the track and enabled more meaningful running, but Mercedes was due to switch its single car between Bottas and Hamilton at that time -- a procedure that requires the seat and pedals to be switched and takes up to an hour.
"With the weather conditions being up and down and the loss of track time we had yesterday, it made sense to keep Valtteri in the car this afternoon," Hamilton explained. "Having run in the morning, he was comfortable in the car already and we would have lost about an hour of running time with the driver switch.
"With no real understanding of whether good weather was coming or not, I took the decision to sacrifice that time in order for the team to gain better understanding of the car by going through the run plan."
Bottas completed a total of 94 laps and the second fastest time with a 1:19.976.
"It was very cold on track today; I don't think I've ever driven in such cold conditions before in Formula One. Testing is always difficult in these temperatures, the tyres are just not made for these conditions.
"But we made the most out of the day. In the morning, we focused on aero work with different aero rakes on the car, running various tests. In the afternoon, I was doing long runs and we also worked on the set-up. It was quite tricky in these temperatures, but we managed to get some work done and found some answers to our testing items.
"The weather is obviously unfortunate, but there's nothing we can do about it and it's the same conditions for everyone. In these conditions, I would say today was a good day. I hope that the weather is going to get better soon and I'm looking forward to tomorrow and Thursday."