Mercedes SLK-350 • Base MSRP: $48,500 • Heating package - $950 (Includes multilevel heated seats and Air-scarf which blows adjustable heated air on occupant's necks)

Cadillac STS • Base MSRP: $40,300 • Premium Luxury Equipment Group - $8,595 (Includes a long list of comfort and performance equipment including heated seats and steering wheel.)

Ford Focus ZX3 SES • Base MSRP: $15,915 • Weather package - $175 (Includes heated seats and side mirrors)

NEW YORK (CNN/Money) - I had to laugh when I figured out the purpose of the button on the steering wheel, the one with a picture of a wheel with wavy lines.

I was driving a Cadillac STS provided by General Motors for a few days of test drives. It had a Northstar V-8, all-wheel drive, adaptive cruise control, heated seats and more stuff I haven't got space to list here.

The heated steering wheel was just silly, I thought.

A couple of days later, already cool temperatures dropped about 15 degrees overnight. After I'd crunched across ice-covered pavement to the car, sat down and turned on the heated driver's seat, I saw that button in an entirely different light.

The heated steering wheel was the best thing ever invented by man.

I wondered if it was detachable so that I could carry it with me on my way to the office. It seemed unfortunate that the top part of the steering wheel, covered in genuine eucalyptus wood, was not heated. But that may have been prevented by the prospect of headlines reading: "Caddies recalled for flaming steering wheels." (Click her for CNN/Money's Pop-up Profile of the Cadillac STS.)

Much attention gets paid to safe driving in winter conditions, a genuinely important topic. But another unfortunate aspect of winter driving is that it's just cold.

Fortunately, for those with enough money to pay for them, auto manufacturers and suppliers have been adding warmth to all kinds of things.

Did you know that only about 13 percent of the energy created by burning gasoline inside your engine actually ends up moving the car? Some 60 percent is simply wasted as heat, which has to be carried off by your car's cooling system.

On Northern winter mornings with single-digit temperatures, "wasted" is probably the wrong word. In the winter, some of that "excess" heat is blown into the passenger compartment to warm up occupants. Few minutes are longer than those spent waiting for the heater to work.

All you who are still living in the age of tailfins and leaded gasoline, please note: cars no longer need to be warmed up for their own benefit. Your car will be just fine if you hop in and drive gently until it reaches normal operating temperature. (Some experts advise letting the engine run for a bout a minute before driving, but no more.) The only point of warming up the car is for the comfort of occupants.

When the weather gets cold, some people go out and start their cars, then go inside to wait for them to warm up. The problem is, when the weather gets cold, thieves start waiting for people to go inside and leave their cars running with the keys in the ignition.

General Motors is offering several models these days with a remote start feature. (According to data from Edmunds.com, this feature, as factory-installed equipment, is unique to GM.)

I was able to stand at a second floor window and, using buttons on the key fob, start a Buick LaCrosse parked outside. With this feature, a car can run for a maximum of 15 minutes, getting nice and toasty. After that, it shuts down unless you insert a key. (Click her for CNN/Money's Pop-up Profile of the Buick LaCrosse.)

If you're you're really, really rich, Maybach sedans offer a system that circulates air and maintain a consistent internal temperature while the car is parked. The system works for about 15 or 20 minutes, said Michelle Murad, a spokeswoman for Maybach, whose prices start at about $300,000.

Maybachs also offer heated seats, of course. Not to mention the massage function. And the gentle jets of air that blow out through tiny holes covering the entire seating surface. But that's another story.

Heated seats are also increasingly common as optional equipment on even low-priced cars like the Chevrolet Cobalt and Ford Focus. The major differences between fancy and routine are how many people inside the car get to enjoy heated seats and how many parts actually get hot.

Sometimes, heated seats are offered only for front seat occupants or just the driver. Other times, they are offered in both front and back seats. Sometimes, only the seat portion -- the part you sit on -- is heated. On nicer cars, the entire seating surface is heated, including the back.

Now, that's more like it.

The Mercedes-Benz SLK 350, a two-seat sports car with a hard convertible top, adds a feature known as the "air scarf." The air scarf circulates warm air around the occupants' necks. That doesn't sound like much, but as autumn turns into winter it can mean extra weeks with the top down.

Looking for more insight on the heat-retention capabilities of the super-wealthy, I called Bob Austin, U.S. spokesperson for Rolls-Royce, and asked him what Rolls owners have to keep them toasty on cold winter days.

"What they have," he told me, "is a home somewhere else."

A pricey option, but it works nicely.