The straight six in the first BMW M5 supersedans was silky smooth and plenty powerful, but it was getting a bit long-in-the-tooth, so it had to go. It was replaced by the 400 hp V8 in the E39, then later with the fire-breathing V10 in the current M5 (above) that pushed horsepower into the stratosphere, particularly when you activated the 'M' button. That engine remains powerful, but with CO2 concerns, fuel economy standards and the fact that the V10 isn't available in much of anything else in BMW's lineup, it seems like the next-gen M5 will probably find its motive power supplied by a V8 instead. If a V8 is good enough for the Audi RS6 and Cadillac CTS-V, perhaps it's good enough for the BMW M5, too.
We saw speculation about a V8 M5 as far back as May, 2008, and more recent speculation that it was going to be a twin-turbo V10 instead, but now Inside Line is reporting that BMW reps have confirmed that a V8 will indeed be in the next M5's engine bay – although they didn't confirm which one. Most likely, it will be the 4.4-liter turbocharged V8 that first appeared in the X5M and X6M. With 555 horsepower and 500 pound-feet of torque, it falls right in the ballpark with other supersedan outputs. That new powerplant will sit in a new cradle as well, with the all-new 5-Series just months away. Around these parts, we're starting to refer to this next generation M5 as the Goldilocks Edition. Six wasn't enough, ten was too much and eight is just right. Thanks for the tip, Derick!
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[Source: Inside Line]