In the early days of its existence, the car was an irritable beast, a machine that brawled its way down the road and threatened to kill you at every turn. The rough edges began to soften when the twentieth century hit puberty; threat and grime were replaced by comfort and reliability. And now, after a century of glorious evolution, we have arrived at a happy point where the phrase "fast car" isn't synonymous with recklessness. Today we have the 2010 Audi S4, the world's friendliest beast.

Some people pine for the loss of the raw, but the S4 is a 333-hp reminder of the joys of subtlety. It is built on the bones of Audi's excellent fourth-generation A4, and while it's both faster and more powerful than its base-model brethren, it looks little different. At a glance, it appears to be upstaged by the previous S4, a V-8-powered hooligan that offered wilder looks, two more cylinders, and seven more horsepower. That car also cost nearly five grand more than the new S4, which starts at $45,900. Something, you think, must be missing.

Or: This is what technological progress actually looks like. In the search for fuel economy and space efficiency, Audi ditched the previous S4's 4.2-liter V-8 in favor of a 3.0-liter, Eaton-supercharged V-6. The six is lighter than the eight and almost as smooth, gets an estimated 27 mpg, and rips to its 7,000 rpm redline with all the racket of a dead cat. Audi's quattro all-wheel-drive system is standard, as is a six-speed manual transmission, and both are so slick and polished as to make you feel unnecessary. Around town, the Audi simply disappears.

But because the S4 oozes cold indifference, you find yourself caning it in search of a response. Remarkably, that's when the Audi awakes: The steering comes alive with feel, the once brittle suspension turns fluid and forgiving, and the distant, soulless engine seems appropriately dispassionate, like an exacting, eminently German tool of war. The car is about to get into a bar fight with some asphalt, and it wants you to throw the first punch.

This is what a sport sedan should be: calm when you need it, sharp when you don't, and sedate enough to fool the neighbors.

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