Net Gains: Don't Trade in That Gas-Guzzler Yet

Trading in your car for a fuel-efficient model might cost more than you think.

ByABC News
May 27, 2008, 3:34 PM

May 28, 2008 — -- Three years ago, gasoline in the United States cost a little more than $2 a gallon.

That seemed high at the time, but it didn't stop many car buyers from purchasing an eight-cylinder SUV or six-cylinder sedan. Now that a fill-up can cost $80 or more, those 2005 buyers might be thinking of trading down to a new, smaller vehicle in the hope of saving money.

They may want to wait a few more years.

Even if gasoline hits $5 a gallon, the savings at the pump are unlikely to make up for the cost of buying a new vehicle featuring better fuel efficiency, according to a recently published study by Consumer Reports magazine.

The review of various trade-in scenarios "shows that it's less expensive to tough out another year or two with a gas-guzzler than to trade in too early."

For example, the Consumer Reports study shows that at $3.75 a gallon for gasoline, an eight-cylinder 2005 Chrysler 300C sedan costs 70 cents per mile to operate, compared to 84 cents a mile for a four-cylinder 2008 Nissan Altima. That 20 percent different exists even though the Chrysler 300C gets 16 miles per gallon compared to the Altima's 25 miles per gallon.

Those figures are based on 12,000 miles driven in the next 12 months and assume the purchase of a new vehicle rather than a used one. The study is available online at ConsumerReports.org.

The two factors that drive the finding that often it is cheaper to keep a gas guzzler than trade down to a more fuel-efficient vehicle are auto-loan interest costs and depreciation.

Interest charges account for the bulk of a monthly payment in the early years of a loan and decline over time. That means if you trade in your vehicle a fraction of the way through the repayment period, the balance owed could still be quite high, even higher than what you owe on the loan. That would leave you with little or nothing to put down on a new, smaller vehicle.

Depreciation, the second factor behind Consumer Reports' findings, is the value an auto loses over time. That happens most rapidly during their first few years as the value of the vehicle plummets by thousands of dollars each year. Consumer Reports estimates that depreciation accounts for 48 percent of an owner's total costs in the first five years, while fuel costs account for about 21 percent. Depreciation levels off after about three years.