For all you diesel tech geeks out there, below is a more complete breakdown of the BMW Advanced Diesel with BluePerformance technology direct from BMW:

Most advanced exhaust gas management: SCR catalyst with AdBlue injection.

To optimize emission management, Advanced Diesel with BluePerformance incorporates an oxidation catalyst placed just downstream of the exhaust manifold, a diesel particulates filter housed in the same unit and an SCR catalyst with the urea injection. In addition to filtering out even the smallest particles from the flow of exhaust gases, this combination ensures effective reduction of nitric oxides (NOX) by way of a chemical reaction within the exhaust system initiated by the injection of a small dose of urea referred to as AdBlue. The ammonia (NH3) generated in this process within the SCR catalyst subsequently converts the nitric oxides (NO and, respectively, NO2) in the exhaust gas into environmentally compatible nitrogen (N2) and vapor (H2O).

AdBlue technology by BMW: Optimized emissions without requiring additional maintenance.

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 12.2 degrees F, 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 U.S. benefit from The BMW Maintenance Program, the refilling of the AdBlue tanks will be a no-charge service for four years or 50,000 miles.

AdBlue from the active tank is delivered to the dosing valve and atomize into the exhaust system. Consistent distribution of AdBlue within the flow of exhaust is ensured by the SCR mixer. The ammonia generated in the hot exhaust flow subsequently acts as a reduction agent in the SCR catalyst and converts environmentally harmful nitric oxides into nitrogen and water vapor in a process referred to as a selective catalytic reaction (SCR). This process gives the special SCR catalyst its name.

The control of the SCR system is masterminded by BMW's powerful engine-management computer. A nitric oxide sensor downstream of the SCR catalyst provides feedback on the concentration of NOX in the exhaust emissions.

Due to packaging limitations in certain vehicles, the position and location of the AdBlue tank may be varied from one vehicle model to the other. In the BMW 335d, the active and passive tank are at the rear end of the car, while in the BMW X5 xDrive35d, the active tank is housed in the front right section of the engine compartment, and the passive tank is under the floor next to the transmission.