Speaking of green, how's the SUV doing?

REED SAXON/The Associated Press

Fueling an SUV is pricey. But the debt for a new vehicle might surpass savings in gas costs, an analyst says.

I know. I know. These are tough times for big trucks.

But even if you nearly choked on that last $100 fill-up of the Tahoe, or the Expedition or the Armada, you might want to postpone any drastic action, according to Kelley Blue Book (www.kbb.com).

The cost of selling your sport-ute may outweigh any gains. The SUV market has declined more than 8 percent since September, with a typical drop in SUV values of $3,000 to $5,000 – which buys a lot of gas even at Big Oil's highly inflated prices.

If your truck is not paid off and you want to sell it, check the most recent trade-in values, because it may be worth far less than you had thought, says Jack Nerad, executive market analyst for Kelley Blue Book and kbb.com.

Then do the math. The debt for a new vehicle might far surpass any savings in fuel costs, Mr. Nerad says.

Eight percent depreciation, by the way, is a drop normally seen in 12 to 18 months. But Mr. Nerad says values may be getting close to bottoming out – perhaps another reason to proceed slowly.

"Large SUVs and SUVs with four-wheel drive are nearing their minimum price points, so we expect depreciation will slow, and we anticipate there will be an uptick in buyers' interest in SUVs as we approach winter. Hanging on to your current vehicle and riding out the current gas prices could be the most economical answer."