The Frenchman was unhappy with how long it took Haas to get on top of its problems in Mexico, where both cars dropped out in Q1 and finished at the back of the field. In Brazil, Grosjean was 15th in each of the three practice sessions before pulling out an impressive performance to take seventh on the grid.
Asked if the result was unexpected, Grosjean replied: “Pretty much.
"We did the plan for qualifying, we knew the cut-off between Q1 and Q2. I knew that my lap was not so good in FP3 so I looked at [Jolyon] Palmer’s time, he was eighth or ninth, he was only three tenths from me and I thought ‘that’s quite easy to get’.
"Somehow I knew we had some potential but on the other hand you look at all the competitiveness throughout the weekend, we’ve been 15th so it wasn’t clear where to go.
"The first run in Q1 felt really good, the second one felt really bad, so I was a bit worried. In Q2 we got a bit better and in Q3 again we managed to understand a bit more. Clearly struggling with the tyres, to get them to work.
"[Friday] was very warm, it was very difficult for us. [Saturday] was cooler, it was better for us. There’s just a lot of study to be done on background because the truth of one day is not the one from the next day.”
And Grosjeans says it is the fluctuations in form which Haas needs to prioritise getting on top of.
“Yes, it’s something we need to understand because the first thing I say in winter testing is that the stability of the car and the traction were the strengths and you could do very consistent lap times without having any problems," Grosjean said.
"It was the case initially in the year and then we had problems and then we changed chassis and came back to better and now we are struggling again. Where does it come from? We don’t really know.
“[Friday] was a good example, there were a few snaps that we could explain; rear locking or too much aero balance. But a few of the snaps we cannot explain like [in FP3] coming into Turn 4 - we have no explanation.
"I had to abort the lap from Turn 6 because I lost the rear, again we don’t have any explanation. There’s a few bits and pieces we need to put together and analyse, where to do, what to do, to make sure the car comes back to a more consistent level."