2012 BMW M5: 560 Horsepower vs 553 Horsepower

So there's been some confusion with the 2012 BMW M5 and its horsepower rating. Some people are reporting 553 horsepower, others 560. 560 is bigger and puts the M5 above the CTS-V in the horsepower war. The genesis of the confusion stems from two things: 1) The first information released was leaked and incomplete. 2) The information released was, primarily, in European units of measure. This means kW and DIN horsepower instead of the way we like it. The two numbers in question were 553 (or 552 -- more on this later) or 560.

560 was the number released by the press kit alongside the 412 kW rating. 412 kW maths itself out to be 552.5 horsepower -- round how you will. Fine, we blame DIN. But then the US press kit came out touting-- wait for it -- 560 horsepower and 412 kW. Sigh.

So what gives? Our engineering guru Jay Kav splains it after the jump.

Horsepower is a devilish thing since not all horsepower is measured using the same yardstick. Ferrari uses Cavallero (CV); the Germans like DIN; the Japanese have in the past used a JIS standard. Yeesh.

We at InsideLine ignore such foreign horsepower ratings. To come up with a horsepower number that is equivalent to SAE horsepower, we have to dig a little deeper.

Instead of using whatever is supplied, we look for the power as reported in metric units known as kilowatts (kW). Kilowatts are the standard in the world of power measurement, but nobody in Americaland thinks in kilowatts. So we convert kW to SAE-sized horsepower.

Do this to the 2012 BMW M5’s rated power – 412 kW – and you get 553 hp. BMW claims 560 hp, even in US guise. So we called BMW to clarify. It turns out that the new M5 will, indeed, produce 560 hp (SAE) and not 553. It’s a similar situation with the company’s X5 M engine, which is rated at 555 hp worldwide, kilowatt rating --408-- be damned.