You just brought home that shiny, new sport utility vehicle. Who's watching what it will be worth two or three years from now?

John A. Blair, vice president and general manager of Automotive Lease Guide in Santa Barbara, Calif., is. And so is Charlie Vogelheim, editor of the well-known Kelley Blue Book of Irvine, Calif.

And so should you, especially if you're leasing or planning to sell after a short period.

Depreciation is the single biggest cost of a new vehicle in the first five years of ownership and now accounts, on average, for one-third of the cost of owning a new car or truck in those early years, according to automotive researcher IntelliChoice Inc. of Campbell, Calif.

Depreciation rates do vary.

For example, if your new sport utility is a 1999 Jeep Grand Cherokee Limited with four-wheel drive, the September-October ALG guide projects it will retain 58 percent of its value over the next two years. That's one percentage point higher than a 1999 Ford Explorer Eddie Bauer.

But if your new sport utility is a 1999 Mercedes-Benz ML320 or ML430, it's expected to retain 71 percent of its value after two years, according to ALG.

The company's guides, which contain projected residual values, are used by banks, leasing companies and others who must gauge how much value is going to be left in a vehicle as time passes.

Blair explains the M-Class, a hot seller that came on the market a year ago as Mercedes' first SUV, benefits because "there's very high demand, low, relatively speaking, production and it's being very popularly received in the market."

He adds that Mercedes vehicles, in general, tend to hold values well because Mercedes officials "tend not to change their vehicles quickly," which helps current models retain value.

Vogelheim, whose company has been publishing resale and trade-in values on used cars since 1926 and whose Blue Book is the "most popular automotive book in the United States," says a new vehicle's market success plays a large role in how well it holds value.

"That which is going to have the greatest resale is that which is going to have the broadest appeal," he says, adding this helps explain the strong resale values for the Honda Accord and Toyota Camry models.

Both have ranked for years as top-selling new cars, with high demand. Over time, they've earned reputations for reliability and durability, too, which strengthens their resale prices as well.

In recent years, vehicles from many foreign-based carmakers have fared exceptionally well in residual values.

For example, a 1999 Dodge Neon coupe has a projected 48 percent residual value over two years and 41 percent over three years, according to ALG. A 1999 Honda Civic HX coupe is pegged at 59 percent over two years and 53 percent over three.

Note that these values typically play into the lease payments a consumer pays, since in a lease, a consumer is paying for the depreciation incurred on the vehicle during the lease term. So, less depreciation can mean a smaller lease payment, unless the lease is subsidized by the auto manufacturer.

Even if you own the vehicle and expect to resell it yourself, you should know that simply buying a good seller isn't the only issue. What you, the buyer, put on the car in terms of equipment, has an impact, too.

"More people want an automatic than a five-speed," Vogelheim says. "More people want a white car than a purple car. More people want a car with air conditioning than one without it."

On the other hand, he says, the equipment on a car "must be vehicle-appropriate."

He explains that "a very expensive sound system would be lost" in a low-priced, subcompact car, like a Hyundai, because buyers don't expect, nor demand, such equipment in that kind of car.

But Tom Metzger, vice president of sales for Asia/Pacific at Harman International, an audio supplier to Toyota, Jaguar, Saab and BMW, notes on higher-end cars, quality sound systems can be a good investment and add to the resale value.

Vogelheim also says "appearance packages are going to be hit or miss."

They may have some regional appeal but it's difficult to gauge, he says.

Blair agrees, saying putting a "gold package" on your vehicle might not return much when you get rid of the vehicle.

Vogelheim notes some vehicles don't necessarily fit into the "broad appeal" category but still do well in retaining value.

Example: The New Beetle. In the latest ALG guide, a gasoline-powered, 1998 Beetle is estimated to hold 70 percent of its value over its first two years.