Soaring gasoline prices led Susan A. Sylvest to consider giving up her 2007 GMC Yukon -- fondly named "Betsy" -- for a smaller vehicle.
"At first blush, it seems like a really great idea -- sell my beast and buy a puppy," said Sylvest, who makes a 45-mile round-trip commute daily from her Coppell, Texas, home to her Dallas office.
But after crunching the numbers, Sylvest, a partner at financial planning firm Murphy & Sylvest LLC, discovered the savings she would derive from driving a more fuel-efficient vehicle would be outweighed by several costlier factors. So she's sticking with Betsy.
Many consumers may be contemplating a similar change as gasoline prices continue their often-daily march upward in the face of turmoil in the Middle East. But even when gas hits $4 a gallon and fill-ups cost $100, most consumers should resist the urge to quickly trade in their gas guzzler on a small vehicle, several experts said.
"If you have a large SUV and are wondering whether to trade it, I would say absolutely not unless something dramatic has changed in your life -- like the miles you drive daily," said Jesse Toprak, vice president of industry trends and insight at TrueCar.com. "You're trying to buy something that's hot and trade something that's not -- which is not a good scenario."
Do the math, say the experts, and factor in more than just gas costs. Take what you pay monthly for your current vehicle, including insurance, and compare it with the monthly costs of a new vehicle.
Say you drive a Suburban that averages 15 miles per gallon and you commute a total of 30 miles daily to and from work. At $4 a gallon, your daily gas cost is $8.
If you traded the Suburban for a small sedan that averaged 30 mpg -- probably accepting too little for the Suburban and paying too much for the economy car -- your total gas savings would be $4 a day, about the cost of a Starbucks coffee.
And you'd no doubt also be facing a monthly car payment and higher insurance costs.
"If you have a 5-year-old SUV that's worth $10,000, one temptation might be to buy a really fuel-efficient car for $20,000, but you're spending an extra $10,000, plus your insurance costs might go up, plus you might be financing," said Jeff Bartlett, online deputy editor for Consumer Reports.
"A new car may provide better safety and it may be more reliable, but that $10,000 -- if money is the whole motivation for doing this -- can buy an awful lot of gasoline."
Here are some factors you need to consider before dumping your gas guzzler for a smaller vehicle:
Monthly payments: "Buying a new car will bring monthly car payments with it," said Greg McBride, senior financial analyst at Bankrate.com. "If you borrow at low interest rates, the gas savings can offset the interest costs pretty quickly, but from a cash-flow basis, you've got this new car payment for the next five years instead of the vehicle you owned free and clear."
Even if you plan to buy a small car with cash, you'd be out that money.
If you're still making loan payments on your vehicle or are leasing, making the move to a small car could leave you owing more on your vehicle than it's worth.
If someone owned, for example, a 2009 Chevrolet Tahoe and paid about $40,000 for it, the vehicle would be worth about $25,000 after 18 months, according to Kelley Blue Book. A midlevel Toyota Prius -- the vehicle many people associate with great economy -- starts at $24,000 before taxes, title and license.
With a typical 10 percent down payment, the Tahoe owner would still owe about $30,000, a difference of at least $6,000 between the Tahoe and Prius that the owner would have to make up or stack onto the Prius loan.
"In most cases, you will not save enough money in gasoline to justify going upside down on your new car," said Thomas E. Murphy, certified financial planner and Sylvest's business partner.
Additionally, while most people view hybrids as the ultimate in auto fuel efficiency, a recent analysis by CarGurus concludes that gas prices would have to hit $7 a gallon to offset hybrids' high price.
Price fluctuations: Rapid increases in fuel costs are typically followed by swift declines, said Jerry Reynolds, a former Ford dealer who hosts an automotive radio show.
Consumers who "panic-trade" a large vehicle such as an SUV for a small one often regret it, he said, frequently trading back into large vehicles when gas prices fall.
And they typically lose thousands on both transactions, "which will buy one heck of a lot of gas," Reynolds said.
"I tell people don't do it," he said.
Last week, a Los Angeles listener said she intended to trade her gas guzzler for a sipper.
"She was planning a big trade down and finally realized that she would save $100 a month in fuel and pay $200 more in new-car payments and insurance," said Reynolds.
Car insurance: New vehicles generally cost more to insure than older ones because the value of the new car is higher. Also, auto lenders' requirements that new car owners carry collision coverage -- which experts advise you to drop on an older vehicle -- will push insurance costs higher.
Reed said consumers could see their insurance costs as much as double with the purchase of a new vehicle.
So before you buy a new car, ask your insurance representative how much it would cost to insure it.
So is it worth it, particularly for a situation that most believe is short-term? Probably not, say most experts.
"A knee-jerk reaction in trading in a car could lead to deep regret if gas prices go down in a year because you will have spent so much money," said Bartlett of Consumer Reports. "And really, the whole goal was to save the money."