The dreaded moment is inevitable: Old Reliable just isn’t so reliable anymore, so you banish it to the netherworld of the used-car market.

Having discovered your old vehicle was worth next to nothing, you vow to do better. This time you should look for a new car that will hold its value. Or should you? Maybe the best deal is a car WITH lousy resale value.

This, of course, is not the conclusion reached by the folks at Kelley Blue Book, the storied guide to used car prices. The other day, Kelley released a list of 2005 models expected to best hold their value for the next five years.

After half a decade of service, the typical car has lost 65 percent of its value. But these 10 should lose only 50 percent: Acura TL, BMW 5 Series, Infinity G35 Coupe, Lexus GX 470, Mazda RX-8, Mercedes Benz CLK 320 Cabriolet, Mini Cooper, Nissan 350 Z, Porshe Cayenne, Volvo XC90.

Bottom line: Most are high-priced luxury vehicles. In other words, buying a luxury car looks to be financially sound.

But some elementary arithmetic shows that’s not so. Buy a $50,000 car with high resale value and after five years you’ll have lost $25,000. Buy a $25,000 car that loses 65 percent of its value, and you’ll lose just $16,250.

Consider the higher insurance and the cost gap gets even wider. Not to mention lost investment return on the extra $25,000 tied up in a fancy car.

When you buy a new car, your losses begin the instant you drive off the lot.

A number of factors are key to the supply-demand equation that determines resale value. Cars that have big production runs and aren’t considered desirable depreciate faster. Cars that are common rentals, have high maintenance costs or designs that don’t age well have poor resale value.

Power windows and door locks, tilt steering wheels, cruise control, sound systems, automatic braking … all boost resale value.

What cars are expected to have the greatest depreciation over the next five years? Pontiac Aztec, Chrysler Sebring Sedan, Jaguar X-Types, Mitsubishi Diamante, Mercury Sable and the Suzuki Vitara.

Consider that humble Sable. I happen to own a 1995 Sable wagon. It is not particularly sexy and is now worth about $1,800. But it’s been pretty trouble-free car. The biggest expense was a recent transmission rebuild, but that didn’t come until well over 80,000 miles. The thing has years of life left.

From this perspective, vehicles with high depreciation may offer the best deals, assuming you buy them used.

Say you buy a modest car that’s five years old and has lost 65 percent of its monetary value. You get it for $8,750 instead of $25,000.

Assume it’s gone 50,000 miles and can go another 50,000 before repair costs get out of hand and you junk it as worthless. That’s 17.5 cents a mile. It’s a third of what you’d pay if you bought a $50,000 high-resale vehicle that will be traded in after five years. This car will lose $25,000 and cost you 50 cents a mile.

High depreciation is good – so long as it comes out of someone else’s pocket.