See also:

Capacities
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Drive away without delay
Do not wait for the engine to warm up while the vehicle remains stationary. Start driving right away, but at moderate engine speeds. This is the fastest way for the cold engine to reach its oper ...

Fuel tank capacity
Approx. 22.5 US gallons/85 liters, including the reserve capacity of approx. 2.1 US gallons/8 liters. X5 xDrive50i/X6 xDrive50i: reserve capacity of approx. 3.2 gallons/12 liters. Refuel promp ...