Seeking to prevent one of the most common and potentially most damaging slip-ups encountered by the owners of diesel-powered vehicles, BMW has become the first manufacturer to equip the filler necks on all of the fuel tanks of new diesels with a unique Incorrect Fueling Protection System. Fitted to the 335d and X5 xDrive35d here in the U.S., this innovative lockout stops anyone from inadvertently grabbing the wrong pump hose and filling up with gasoline rather than diesel. Under the best of circumstances, making that mistake will only result in a pricy purging and cleaning regimen for the entire fuel and filter systems. At worst, it can cause plenty of far costlier internal damage to the engine.
Luckily, this is a one-way problem, as the larger diameter on diesel fuel nozzles already precludes them from being inserted into the tank filler neck of a vehicle that burns gasoline. However, the fact that today's modern diesels tend to sound and perform so much like their gasoline-powered kin has led more and more owners -- especially those who regularly drive vehicles powered by both kinds of engines -- to accidently select the wrong hose with increasing frequency.
With BMW's lockout system, a safety flap positioned at the opening of the tank's filler neck is only permitted to swing clear when the bigger diesel fuel nozzle makes contact with a pair of electronically activated pins. The system also is designed to prevent similar kinds of miscues when the refueling process is done by using a spare emergency can instead of at a commercial pump.