Red Bull and Toro Rosso are not yet working with their respective engine suppliers for the 2007 season.
Toro Rosso ran at the Barcelona test this week with its usual Cosworth V10 setup, despite inking a deal to use Ferrari power next year.
“We have tested with the 2006 STR1 (car) and the Cosworth engine,” a spokeswoman confirmed on Friday.
“We do not know yet when the new STR2-Ferrari will be ready to be tested.”
Sister squad Red Bull Racing, meanwhile, will use the title winning Renault V8 next season, but had to be content with its usual Ferrari engines at Circuit de Catalunya as the new agreement does not begin until the New Year.
In contrast, the formerly Cosworth-powered team Williams is already testing its new Toyota units.
“The (Red Bull) agreement has had an impact on the structure of our trackside support operations,” Renault’s engine chief Rob White said, “as we prepare to run four engines at every race and test rather than just two.
“Those changes are now being finalised, with a view to the beginning of our engine supply agreement in January 2007.”