BMW Sauber technical director Willy Rampf is hopeful that the update package the team has brought to this weekend's European Grand Prix will be worth at least two tenths of a second.
But despite the improvement in laptime from the changes, which include a new lighter chassis for both Robert Kubica and Nick Heidfeld, Rampf is unsure whether it will allow the team to take a major step forward in terms of overall position.
"It should be worth a few tenths here," Rampf told AUTOSPORT. "In previous years, with a step like this we would have made a big step in the ranking. But everyone brings updates and it's amazing the progress that everyone is making.
"Here we have a lot of new parts. We have a new engine cover with sidepods that are more tight, a different floor and also a new lightweight chassis."
Rampf stressed that the team's development has not been affected by BMW's decision to withdraw from F1 at the end of the season, and that the team is still on course to launch a major aerodynamic update for next month's Singapore Grand Prix.
"We are continuing with the planned development and everything that is in progress," said Rampf. "We will have another aerodynamic package for Singapore and more updates in between. We are still doing the normal aerodynamic development.
"It's hard to say what the Singapore package will achieve because it is still in the windtunnel but overall we have made some big steps this year."