This year's higher gasoline prices are prompting drivers to switch to smaller, more fuel-efficient cars. The trouble is, some of the money they save may be going to higher insurance premiums.

Small cars generally cost more to insure than larger ones because they're involved in more accidents and incur bigger claims, especially for injuries. That's true regardless of the driver profile, though younger and less-experienced drivers tend to buy smaller, cheaper cars.

A 40-year-old male driver would pay an average of $1,704 to insure a 2009 Mini Cooper that gets 37 miles per gallon on the highway, according to a study by Insure.com, an online insurance broker. That same driver would pay only $1,266 — a difference of $438 — to insure a Toyota Sienna Minivan, which gets 23 mpg.

Similarly, a Honda Civic compact that gets 36 mpg on the highway costs $412 more a year to insure than a Honda CR-V, a small sport-utility vehicle that gets 27 mpg. ~ ~

"There is always a safety trade-off when you move from a large, heavy vehicle to a smaller, lighter one," says Russ Rader, a spokesman for the Insurance Institute for Highway Safety, a nonprofit industry-funded group.

Your insurance premium is based in part on the history of your particular model, and small cars often cost less for property-damage liability coverage because they're less likely to damage other cars, says Mr. Rader. But lower property-damage liability costs for small cars are more than offset by most other coverage components, especially personal-injury protection for car occupants.

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