Mercedes have identified the cause of Valtteri Bottas' Spanish Grand Prix retirement, which they say was caused by a new failure they've not witnessed before during a race or during testing.
Bottas was third when he retired from the race, won by team-mate Lewis Hamilton, and it was suspected that his 'old' power unit may have been the cause.
The Finn was forced to revert back to 'PU1' for the event after a water leak was found on his new unit ahead of qualifying. PU1 had already completed the opening four races of the season, and whilst it wasn't near its mileage limit, Bottas, like Hamilton, was scheduled to race with an upgraded unit in Spain.
However the cause of his retirement was actually turbo-related, according to team boss Toto Wolff.
"We’ve identified the root cause of the problem, which was the turbo," explained the Austrian.
"We haven’t seen that defect before, which shows you that you need to be double diligent. This is a technical sport and if you stretch your limits, you’ll encounter technical problems."
Wolff says it was "painful" to lose out on Bottas' points when the championship fight is so close between them and Ferrari.
"It’s always good to come away from a race weekend with a points advantage, no matter how small," he added. "But the gap is just that: very small.
"We are in a massive fight with Ferrari. On one side, this is very exciting and challenging. But on the other side, it is going to stretch us to our limits."
