yeah it could be new oil, they may not have drained it to well...I wouldn't worry about it just find a private mechanic with good rep. next time.

synthetic oil never wears out, just get's dirty. The most important part is the oil filter, Only use the Fleece filters , do not use paper filters in this engine, they will disintegrate or blow out from the very high oil pressure. the pump puts out like over 120 psi at idle no paper ellement will survive this.

They are made by Mann filters, I buy them online at Rockautoparts.com