Will Steger is a man of habit. He always drives a Cadillac, but never spends more than $650 on one. "You can buy the old ones so cheap," he said, "and I usually get over 200,000 miles out of them."

Steger has adopted other interesting codes to live by. He believes in pushing himself to full potential, for example, even if it means going out all day in 70-below-zero cold. But he won't eat his dogs. "No," he said with a smile, "I don't. But even if I did, I wouldn't tell you, would I?"

Steger, 42, a newly minted world-class adventurer, was in Washington last week to push his book, "North to the Pole", which chronicles his recent 55-day voyage to the northernmost place on earth, and to drum up support for his next challenge, an unprecedented, 5,000-mile dogsled traverse of Antarctica starting in August 1989.

With all that cold behind and ahead of him, he was predictably unimpressed by a brisk northwester toppling the hats off pedestrians downtown. While city folks bundled, Steger rambled happily up 15th Street in his rolling, trekker's gait, wearing a Patagonia jersey and no jacket at all.

A slight, serious, bookish-looking fellow in wire-rimmed spectacles, Steger is only about the 12th person to have led a successful overland expedition to the North Pole. Exact numbers are hard to come by because the pole is nongeographical -- a spot without landmarks somewhere on the frozen Arctic Sea. Some claims of its conquest are vigorously disputed.

But no one doubts Steger. When his six-member party, including Ann Bancroft, the first woman ever to trek to the pole, arrived at 90 degrees north latitude on May 1, 1986, the sextant was spot-on. Pilots who flew in to ferry out the travelers confirmed by satellite navigation that, "Somewhere within a couple hundred yards of here is the earth's hinge-pin," as one put it.

Steger's voyage thus became the first confirmed overland trip to the pole without resupply. His party of eight left Ellesmere Island in northernmost Canada with three tons of gear, five sleds and 49 dogs and wound up 500 grueling miles north at the pole with 21 dogs, six people and two pounds of food left.

"That's good planning," said Steger proudly.

Nor did anyone have to eat dogs. Two injured men and the weariest mutts were shipped back on bush planes that intercepted the crew along the way. The planes brought nothing in, not even weather information. So fastidious was he about outside help, Steger wouldn't accept even a sip of hot coffee from a pilot's thermos.

Most modern pole voyages are resupplied by air along the way. Adm. Robert Peary followed roughly the same track as Steger's without resupply on his famous 1909 expedition. Peary used 30 men and 130 dogs on the round trip, but his actual attainment of the pole never was confirmed.

By Steger's engrossing account in "North to the Pole", his was an awesome journey across a hostile moonscape of jumbled ice ridges, watery fissures and horrific, numbing, life-threatening cold, with wind-chill factors below minus-100 degrees Fahrenheit. Only once during the journey did he see any sign of native life -- a set of Arctic fox tracks.

So why, after eight weeks of that, would he want to travel across the other godforsaken end of the planet for seven months?

Steger said he expects the South Pole to be considerably more hospitable because it's land, not frozen salt water. That means he can travel in high summer without worrying about the world melting under him. As a result, temperatures shouldn't dip below minus-40, and during much of the trip will hover around balmy zero.

On the other hand, he said, Antarctica is noted for crevasses that swallow dogsleds and their crews without warning, leaving no trace. The winds there are far fiercer, altitude can pose problems and, with 10 times the distance to cover, the cost of the expedition will hit $8 million, more than 10 times the North Pole budget, which he must raise.

To prepare physically, he and his party of five will trek down Greenland by dogsled, end to end, next summer. He's signed up five adventurers from France, Russia, Japan, England and Canada, although the makeup of the party may change. They will take three sleds and dog teams and arrange resupplies every 500 miles.

The main purpose of the Antarctic mission, Steger said, is to focus attention on its fragility.

"The North Pole represented a personal best," he said, "but I wanted to do something of social importance.

"Antarctica has been protected for almost 30 years by the Antarctic Treaty, one of our finest examples of international cooperation. It says the continent will be used only for peaceful purposes, with no mineral or military exploitation.

"Now," said Steger, "the treaty is up for review in 1991. With that in mind, our goal is to attune the world to what Antarctica is through TV, radio and newspaper coverage, and to expose the danger of its exploitation by private interests."

After which Steger doesn't know what he might do. Maybe just retire for a while to his cabin in the woods near Ely, Minn., and visit with his dogs and old Cadillacs.