2014 BMW 328d xDrive Wagon Long-Term Update 6
Diesel Exhaust Fluid?
While nearing the end of the 328d's stay in the Motor Trend garage, I had a realization: Not once has the car asked for a diesel exhaust fluid (DEF) fill-up. In truth, I had forgotten the car needed the stuff.
Most modern diesel engines use DEF to help reduce tailpipe emissions (NOx specifically). The fluid sits in a separate reservoir and is injected in small amounts into the exhaust stream. When it runs low, the car gives you a warning. Ignore that warning, and the car won't start until the fluid is refilled.
The 328d gives you a warning 1,000 miles before empty -- or so I'm told. I've never seen it. If I did, I'd go to my local dealer, who would top it off for free under BMW's free 4-year/50,000-mile maintenance program. If you're outside of that program window or just a die-hard DIYer, you can buy a gallon of DEF at your local parts store for less than $10 and pour it into the blue-capped nozzle next to the diesel filler neck.
Why hasn't the 328d required a DEF refill? Because BMW refills the reservoir during normal service intervals. This is convenient more than anything else, as DEF isn't expensive. But what's more interesting is the byproduct: This convenient service/fill-up overlap eliminates some of the special care your normal consumer might think about when comparing a diesel engine to a gas engine. It helps eliminate concern.
That concern is easy to point a finger at and mock, but it's worth considering. When the 328d first showed up, for example, I felt I had to scan every gas station for that green sign that denotes diesel availability. After a few months of driving the 328d, I found diesel fuel was available nearly everywhere -- though the quality of some diesel pumps left a bit to be desired.
You can drive the 328d like any other car; it requires no special attention. If it weren't for the small amount of audible clatter, you might just think it was a decently powerful station wagon with great fuel economy and range but a curiously low redline.
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