SAN FRANCISCO (MarketWatch) -- The market for large sport-utility vehicles and trucks is in a sudden free fall as owners confronting potential $100 fill-ups are rushing to unload their petrol pigs to spare themselves squeals of pain at the pump.

The values of many used models have dropped as much as $4,000 below recent "book" prices. Many dealers are offering even less on trade-ins on the least-popular vehicles -- if they'll even take them at all.

The same mass anxiety that gripped Americans driving large, eight-cylinder sedans by the early 1980s and spurred rapid replacement with four-cylinder gas misers is resurfacing with a vengeance. The question many distraught owners need to ask themselves is whether dumping their SUV or minivan is a smart financial move in the long term.

"People need to put pencil to paper to see what it will really cost them, because there are other ways to save on gas costs," says Dale Early, owner of Deerbrook Forest Chrysler Jeep in Kingwood, Texas, and a National Automobile Dealers Association board member.

Before selling off a gas glutton, owners should consider the following to avoid being pennywise and pound foolish:

The cost of a replacement vehicle. Buying a hybrid may seem like a financial lifesaver, but not if your gas guzzler is paid off or soon will be, Early says. Taking on a $400 monthly car payment may put a far more severe crimp in personal cash flow -- nearly $5,000 annually for five or six years -- than the higher annual fuel costs for a large vehicle. If your large vehicle isn't likely to need a major repair in the next few years, you may be better off holding onto it.

Buying a hybrid may seem like a financial lifesaver, but not if your gas guzzler is paid off or soon will be, Early says. Taking on a $400 monthly car payment may put a far more severe crimp in personal cash flow -- nearly $5,000 annually for five or six years -- than the higher annual fuel costs for a large vehicle. If your large vehicle isn't likely to need a major repair in the next few years, you may be better off holding onto it. Limiting usage. If you're in a household with two vehicles and one gets reasonably good gas mileage, you'll save on gas spending by driving that one primarily and leaving your larger vehicle parked as much as possible.

If you're in a household with two vehicles and one gets reasonably good gas mileage, you'll save on gas spending by driving that one primarily and leaving your larger vehicle parked as much as possible. Sell off your other vehicle. If one of your household's vehicles is a midsize sedan or similar fuel-efficient vehicle, consider selling or trading it in instead. You'll get good money for that car rather than taking a massive hit on your larger vehicle's value, and you can use the proceeds to buy a top mileage producer to replace it.

If one of your household's vehicles is a midsize sedan or similar fuel-efficient vehicle, consider selling or trading it in instead. You'll get good money for that car rather than taking a massive hit on your larger vehicle's value, and you can use the proceeds to buy a top mileage producer to replace it. Weather the storm. If gas prices fall or even just level off in the next few months, dealers say the large-vehicle values will likely recover by $1,500 to $2,000 with an easing in our collective anxiety level.

"If gas prices stabilize, SUV values will come back up some. People shouldn't be in a hurry to rush out and take a bath right now," says Chris Martin, president of E-Z Auto in Fayetteville, N.C., chairman of the Carolinas Independent Automobile Dealers Association.

"There's been so much emotion and panic, people aren't really paying attention to the practical options and solutions," Early says. "Getting your brains blown out on a trade-in and paying a premium for a subcompact right now may not be the most economical decision."

In preparation for sale

If you want to get the most for your large vehicle, there are three steps to take before offering it up for a private sale or trade-in, says Marc Cannon, senior vice president for Auto Nation, which owns dealerships in 16 states and sells more than 500,000 cars a year.

As with selling any used vehicle, Cannon says you'll recoup more of what you paid for it if you go to these minimal lengths, though they may entail spending a few out-of-pocket dollars:

Get the vehicle detailed. Even if you don't recover all the money you'll drop on a deep-cleaning and waxing, you'll stand a better chance of attracting a buyer or dealer trade-in if the vehicle is looking its best. Do minor repairs. All the little fixes you've been meaning to get but haven't won't go unnoticed by buyers with numerous choices in a glutted market. Whether it's a busted side-view mirror or replacing two severely worn tires, taking care of easy fixes would be a wise move. Gather all repair records. The more extensively you can document the maintenance and repair work you've had done, the more confident a potential buyer will be that they're getting a reliable vehicle.

"It's the same principle as always -- any vehicle with a lot of eye appeal, in good shape and with decent miles on it will still attract a buyer," Early says.

Current demand

As in any market conditions, certain makes and models are in greater or lesser demand based on their perceived value, reliability record and optional equipment. Here are the vehicles in the SUV, truck and minivan categories for which dealers say demand is holding up best:

SUVs. Large models with a third-row seat capable of accommodating seven passengers remain attractive as family haulers, says Randall Smith, owner of Randall Smith Auto Sales in Dalton, Ga., and chairman of the National Independent Automobile Dealers Association. Smith says two-wheel drive SUVs are holding their value better than their four-wheel or all-wheel drive models because they tend to get slightly better gas mileage, as are SUV models built on car and not truck chassis. On the used market, Cannon says the values of Chevy Tahoes and Suburbans also are faring better than might be expected because "they're a workhorse, especially for hauling boats or travel trailers."

Large models with a third-row seat capable of accommodating seven passengers remain attractive as family haulers, says Randall Smith, owner of Randall Smith Auto Sales in Dalton, Ga., and chairman of the National Independent Automobile Dealers Association. Smith says two-wheel drive SUVs are holding their value better than their four-wheel or all-wheel drive models because they tend to get slightly better gas mileage, as are SUV models built on car and not truck chassis. On the used market, Cannon says the values of Chevy Tahoes and Suburbans also are faring better than might be expected because "they're a workhorse, especially for hauling boats or travel trailers." Trucks. Demand has plummeted for many used trucks as owners who bought them for a lifestyle statement rather than hauling needs bail out for sedans and crossover vehicles. At his Houston-area dealership, Early says new-truck sales were down 40% last month from a year ago -- with eight-cylinder models the biggest losers. "In Texas, trucks and SUVs have been the preferred vehicle of choice for a long time," Early says. "We're now seeing both Bubba and the high-school teacher getting out of the pickup because they can't afford the note, gas and insurance."

Demand has plummeted for many used trucks as owners who bought them for a lifestyle statement rather than hauling needs bail out for sedans and crossover vehicles. At his Houston-area dealership, Early says new-truck sales were down 40% last month from a year ago -- with eight-cylinder models the biggest losers. "In Texas, trucks and SUVs have been the preferred vehicle of choice for a long time," Early says. "We're now seeing both Bubba and the high-school teacher getting out of the pickup because they can't afford the note, gas and insurance." Minivans. Values of these people movers haven't fallen as precipitously as for SUVs and large pickups because they generally get better gas mileage. Yet many families with four or fewer members are starting to part with their minivans in favor of more fuel-efficient, midsize sedans. The most-popular minivans in the used car market -- Honda Odyssey, Toyota Sienna and Chrysler Town & Country -- continue to attract the best resale values, Cannon says.

If you do decide to trade-in your large vehicle, you could make up some of what you lose on the back end with a trade-in on the price of the new vehicle if you opt for something other than the top-mileage models. Due to the soft economy, new-car sales have been sluggish and dealers are eager to unload mounting inventories.

Says Cannon: "There's a real opportunity to negotiate a great deal on a new car right now -- as long as it isn't a hybrid."