I recently got my aero serviced at the dealer and in doing so, I also asked them to change the oil and do an engine flush. Much to my dismay, after getting my car back and asking the technician, I found out that they put semi-synthetic oil in . I asked why they did not use full synthetic but the tech said that the 02's did not call for it. Should I be worried and change it immediately or should I just wait until 3000 miles? I don't drive my car too hard so I'm hoping there is no problem associated with the matter.