Guenther Steiner says the Haas F1 Team intends to "trickle" in new parts every few races, with a new rear wing set to appear at the Spanish Grand Prix this weekend.

The American debutants will also run with its new front wing in Barcelona, after trying it out in China and Russia, and in addition will switch to using Ferraris latest power unit.

"We've made a few changes to the car," said Steiner, ahead of the first European race of the season. "We've got a new front wing that we tested for the first time in China, and we've got a new rear wing that we'll race for the first time in Barcelona.

"We won't have big changes on a set schedule. We'll introduce new parts when we feel we've made enough gains. New parts from our development will trickle in every few races, just like every other team does."

Quizzed on the new front wing, first seen in China, Steiner added: "We started to run with it in China, but we had some other issues to work out [with the tyres] so we decided not to focus on the new front wing. We left the old wing on because we knew that the original wing worked. We re-tested it [again] during FP1 in Russia and both drivers liked it. It makes the car more stable around the track in cornering, so we've decided to use the new wing going forward."

To date, the team has scored points in three of the first four races, and currently sits fifth in the Constructors' with 22 points on the board, something Steiner concedes he did not expect coming into the team's maiden season.

"To be honest, no [achieving that didn't enter my mind]. But we are very happy and we'll take it," he continued.

"The team has developed a lot in these two months from where we were, but it's normal for a new team. It's a very good thing that we're growing and making improvements. We're a lot better team now than we were two months ago. The team has made significant steps."