Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Flight Crew Landed in Emergency Condition; General Declared Emergency
Aircraft
During descent the left engine oil quantity showed six quarts and decreasing as we progressed toward landing. A deadheading pilot confirmed smoke was trailing from the engine with the throttle at idle. We requested a straight in approach.  We briefed the flight attendants and flew a visual approach with the left engine at idle. Upon exiting the runway we shut down the engine; CFR confirmed the engine was secure; and we taxied to the gate.
An A320 flight crew requested assistance and landed straight in at their destination when they determined the left engine was losing oil quantity.