What was found
AIRCRAFT WAS GNDED. OIL FUMES IN CABIN AT TAKEOFF & INITIAL CLIMB. DISSIPATED WITHIN 5 MIN. VERY STRONG ODORS OF OIL IN COCKPIT & FINAL DESCENT & LANDING ROLL OUT, TAXI HAD TO OPEN WINDOW. ACCOMPLISHED JC 26L00021001, TROUBLE SHOT CABIN AIR QUALITY WITH FORM 8533. WHILE STARTING NR 1 ENG MX RECEIVED A MASTER WARNING & CAUTION LIGHT, ABORTED ENG START & INVESTIGATED CAUSE. THEY FOUND THE NR 1 IDG WITH NO OIL IN THE SIGHT GLASS & SERVICED THE IDG, VISUALLY INSPECTED ENG & COWLING FOR EVIDENCE OF AN OIL LEAK WITH NONE FOUND. THE ENG WAS SUCCESSFULLY STARTED, IDG OIL LEVEL WAS STABILIZED & A BRIEF ODOR WAS DETECTED ON ENG START, BUT WENT AWAY & NEVER RETURNED. RETURNED THE ACFT BACK TO SERVICE.