Now we can finally reveal the car, as it has made its debut this week at the 2013 New York Auto Show.
So how does its new 2.0-liter four-cylinder turbodiesel engine do, versus the six-cylinder engine of the previous generation 335d?
Pretty well, actually: it delivers 180 horsepower and 280 pound-feet of torque, and, according to BMW, will return a fuel economy of up to 48 mpg.
By comparison, the 335d’s 3.0-liter six-cylinder turbodiesel engine delivered 265 horsepower and 425 pound-feet of torque, but only got into the mid-30s when it came to fuel economy.
And, despite all of its extra performance, the 335d would only sprint to 60 mph about a second faster than the new 328d, which BMW says will accomplish in roughly 7.2 seconds.
If that wasn't enough, word is that the 328d sedan will share showroom space with a 328d Sport Wagon, too, although that car wasn’t on display in New York and BMW was being tight-lipped on the matter.
For those wanting more grunt, BMW’s latest six-cylinder turbodiesel engine will be appearing eventually in the 5-Series and X5 models.
For more launches and news from the New York Auto Show, head over to our dedicated show page.