"Following the overseas races we have been looking closely at the driver line-up for the Friday of the GP weekends," team boss Mario Theissen said in a BMW preview for next week's Spanish Grand Prix.
"Until further notice the two race drivers will be on track for the whole of Friday."
German Vettel, 19, made a strong debut as Friday test driver last year when all but the top four teams were allowed to run three cars.
The rules have changed for 2007 with only two cars allowed, forcing teams to sideline one of their two race drivers if they want to use a test driver for Friday practice.
BMW are third in the standings after three races but they alone of the top teams had been using a test driver on Friday, a decision that deprived Germany's Nick Heidfeld and Poland's Robert Kubica of track time.
