BUY

The BMW N63 4.4-liter twin-turbo V8 is known for heavy oil consumption, and worn valve-stem seals are the usual cause. On the 550i, 750i/750Li and 650i owners report the engine burning roughly a quart of oil every 750-1,000 miles, often at surprisingly low mileage (one 2016 550i owner reports a quart every 750-800 miles at ~36k). The oil is drawn past hardened valve-stem seals and burned in the cylinders, and the same heat that ages the seals is hard on the turbochargers that live in the engine's hot "V". BMW ran an extended oil-consumption / customer-care program (tied to the N63TU class action) that replaced valve-stem seals and related parts rather than issuing a recall, so this is verified through service history and a dipstick check, not a VIN lookup.

Check — Check the oil level on the dipstick before the test drive and ask how often the seller adds oil between changes; a quart every 1,000 miles or less is the tell. Ask whether the oil-consumption / valve-stem-seal work was performed under BMW's N63 program and get paperwork, and confirm that chronically low oil has not already damaged a turbo. Confirm the car actually has the N63 V8 (the 50i/550i/750i badge), not an N55/N20 six or four.