People who lease cars often make the mistake of not checking their car insurance ratesIt may seem an obvious part of budgeting before you lease or buy a new car: Call your car insurance company to see what your rates will be. But according to LeaseTrader.com, a lot of veteran car shoppers are skipping this crucial step.

When you buy a new car, chances are, your insurance rates aren't going to stay the same (as we point out in our previous article on the cars that cost the most and least to insure). People often upgrade to some better wheels, or their last car was such a junker, that it can be a jolt when suddenly they're paying $50 a month more for car insurance.This is an even bigger problem with car leasing, says John Sternal, spokesman for LeaseTrader.com, an auto lease transfer marketplace. And more people have been leasing, due to the economy, Sternal points out.

According to Edmunds.com, leases made up more than 20% of all new car purchases this year, for the first time in a more than a decade. And with more leasing going on, there are more unhappy customers, since a lot of people aren't familiar with some of the nuances of leasing, such as higher insurance.

"A lot of people don't fully understand how leasing works," says Sternal. "They don't fully understand that they aren't driving their own car. It's the bank's car. So when you lease a car, the bank mandates that you carry a certain type of coverage."

And it's not likely to be coverage on the level of Safe Auto, which brags about keeping you legal for less. More likely, says Sternal, "it'll be everything Progressive offers."

People leasing cars "are shopping with a budget and thinking, 'I can afford $300 or $400 a month,' and reach the top of the budget with their lease," Sternal says. "Then when their auto insurance adjusts, they're out of budget."

In fact, LeaseTrader.com says the number of people trying to get out of their lease because they didn't understand how their new car would affect their car insurance premiums will account for 4.5% of transactions this year, up from 2% in previous years.

Obviously, most people lease because they want to save money; skyrocketing insurance premiums negate that strategy. So if you're considering leasing a car, don't forget to call your insurance company and tell it you're thinking of leasing, say, a Prius and see what the rates are. If they're going to be insane, then obviously you may want to readjust your tastes and opt for driving a lower-priced Kia instead.

Of course, there's also the question of whether you should lease or buy a car. If you're mulling that over, check out WalletPop's lease or buy car calculator.

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