MD-11
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Situational Awareness
Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition
Aircraft
There was a faint smell of oily fumes during departure and cruise which seemed normal since the aircraft had just come out of maintenance.  Upon initial descent into ZZZ; the fumes became much more prevalent.  We donned our oxygen masks [advised] with ATC.  We described our emergency and asked to continue expeditiously to land at ZZZ.  We had no other indications other than the strong smell of fumes.  We continued without further incident and landed safely at ZZZ.  Fire and rescue did a visual inspection of the aircraft as we cleared the runway and permitted taxi to and shutdown at the gate.  The mechanics have been working on the aircraft today.  They cleaned air conditioning ducts and appear to have found the problem within systems on engine number 1.
MD-11 Captain reported strong oily fumes during descent.