Originally Posted by Placey
The urea will be replenished w/ the scheduled maintenance.
Yeah, it seems not a whole lot of the solution is needed..
From BMW Press:
"To introduce AdBlue technology into the car, BMW has developed a two-tank system ensuring convenient use of this new technology with all the benefits and ease required by the customer. The amount of AdBlue required in each case is injected from the active tank (approximately 1.6 gallons in volume) by means of a dosage pump. And since the urea solution would freeze at a temperature of 12.2oF, this active tank, as well as the dosage pipes, are heated.
The active tank is connected to a second reservoir, referred to as the passive tank. With its additional capacity of approximately 4.5 gallons, this passive tank offers a plentiful supply of the urea solution. The average range provided with this supply capacity is indeed sufficient to have the tank system replenished only when the driver needs to change the engine oil.
Hence, the large amount of AdBlue stored in the reservoir enables the customer to enjoy continuous driving, without having to change his/her service intervals. The driver therefore benefits from the advantages of this environmentally friendly emission technology throughout the entire running life of the car, without any additional service or visits to the workshop. Since all BMWs sold in the US benefit from The BMW Maintenance Program, the refilling of the AdBlue tanks will be a no-charge service for 4 years or 50,000 miles."