What can the Tesla Model S autopilot really do?

In the end, the online rumors proved to be largely accurate.

Last night, Tesla Motors CEO Elon Musk revealed an all-wheel-drive version of the Tesla Model S electric luxury car--known as 'D'--whose most powerful P85D version will accelerate from 0 to 60 mph in just 3.2 seconds.

That makes it the fastest four-door car in the world.

The AWD version adds highway range: The Model S '85D' version with an 85-kilowatt-hour battery pack has 295 miles of range (at 65 mph), the 'P85D' has 275 miles, and the '60D' has 225 miles. (Official EPA combined range figures aren't yet out.)

Musk also announced an 'Autopilot' feature for the Model S that will change lanes for the driver once the signal is turned on, assuming the car deems it safe to do so.

It warns drivers when they exceed the prevailing speed limit as well, a feature that had already been largely revealed by recent Tesla owners.

Of those features, only the additional range and the automated lane-changing feature hadn't previously been predicted online.

Dual motor AWD

Adding a second electric motor to the front axle of the Model S reduces the front trunk space under the car's hood, but development work was presumably shared with Tesla's upcoming AWD Model X crossover.

On the highest-spec model, the P85D ('P' for Performance, 'D' for Dual motor), the rear motor is rated at 470 horsepower and the front at 221 hp, for a combined output of 691 hp.

That's among the highest for any four-door vehicle in the world, exceeded only by the recently announced 2015 Dodge Charger SRT Hellcat's 707 hp.

And the Tesla's 0-to-60-mph time of 3.2 seconds equals or beats the Charger Hellcat's, quoted at the "mid 3 seconds".

The Dodge is quicker through the quarter-mile--11.2 seconds versus 11.8 for the Model S P85D--and has a top speed verging on 200 mph, against the Tesla's 155 mph.

On price, however, gasoline beats electricity at the moment: The top Tesla starts at $120,000, while the 2015 Charger SRT Hellcat stickers at just $61,000.

Specifying Dual-motor all-wheel drive on any model except the P85D--it's available on all versions--boosts the bottom-line price by $4,000.

Autopilot: More features in future

The suite of features collectively dubbed Autopilot are based on a forward-looking camera, a radar sensor, and ultrasonic sensors giving a 360-degree field around the Model S.

The hardware for this system has been included in all Teslas built starting two weeks ago, but unlike software updates, it cannot be retrofitted to older Model S vehicles.

Today, the Autopilot feature reads roadside speed-limit signs, and if the driver allows it to do so, keeps the car at the posted speed limit.

When the driver switches on a turn signal, it will also automatically change lanes if a space is free.

The lane-changing is the only feature not already available on a variety of luxury competitors.

But Tesla promises additional features will be added to the Autopilot system in the future, using the sensor data for further driving assistance that will gradually bring the Model S closer to autonomous driving under some conditions.

The Tech package with Autopilot adds $4,250 to the cost of a new Tesla Model S.

Deliveries of the P85D start in December, with the 60D and 85D to follow in February.

Trade-in path

Discussion about Tesla's latest announcements includes the notion that the new AWD version provides a clear reason for owners of two- or three-year-old Tesla Model Scars to trade them in for new ones.

That would neatly fit into Tesla's foray next year into providing Certified Previously Owned (CPO) used Tesla Model S cars as well as selling new cars.

Meanwhile, no mention was made last night of the much-delayed Tesla Model X electric crossover utility vehicle.

Insiders suggest that the production version of that car will be unveiled late this year or early next year.

The Model X is now supposed to go into volume production sometime next spring or summer.