Kevin Magnussen says Haas is not getting overtly excited over the pace it displayed during the second pre-season test at the Circuit de Barcelona-Catalunya.
Haas is entering its third season in Formula 1, having placed eighth in the standings in both 2016 and 2017, with its VF-18 an evolution of its predecessor.
Magnussen and Grosjean placed sixth and ninth respectively on the combined leaderboard, with their best lap times coming on the Supersofts, rather than the Hypersofts or Ultrasofts.
When asked whether Haas could spring a surprise, Magnussen replied: “We have to wait and see. We don’t know what other people can do, or if other people have a lot of fuel in the car.
“So we are not getting excited already. We feel like we have improved our car, and we definitely have improved our car, but so has everyone else.
“We will have to wait until Melbourne to really get a better idea of where we are going to be, and then the first couple of races will probably show another picture.
“Hopefully we can do well, but it is too early to say now.”
Magnussen expanded on Haas’ ambitions for the 2018 campaign, reiterating that moving one spot up the Constructors’ championship is a realistic target, after its pair of eighths.
“We are going into this season with a mind-set that we will do the best we can,” he said. “And not have any set expectations.
“We don’t necessarily need to finish fourth, we need to not do worse than we did last year.
“We have a pretty common goal in the team that we want to take a step forward in the field and preferably move up a position in the championship.
“Our goal is to try not finish eighth again. If we can finish seventh in the constructor’s championship and move up a position we can be really happy.
“We are pleased with where we are in the process right now, and we will take it race by race.”