Don’t ditch your gas-guzzling clunker by the roadside.

Instead, swap it for a new, more fuel-efficient vehicle and you can get some help from the federal government.

The so-called “cash-for-clunkers law,” signed June 24 by President Barack Obama, is a means of jump-starting new vehicle sales and encouraging consumers to purchase clean, fuel-efficient vehicles.

Though the law takes effect today, it may take a few more weeks before the National Highway Traffic Safety Administration adopts the final regulations and local new car dealerships make assistance available.

Under the program, eligible clunkers include passenger cars and light trucks that are model year 1984 and newer that get no more than 18 miles per gallon city and highway combined. For cars, the credit value will be $3,500 if the new vehicle gets at least 4 miles per gallon more than the clunker or $4,500 if it gets at least 10 mpg more. For light trucks, the credit value will be $3,500 if the new truck gets at least 2 mpg more than the vehicle being traded in or $4,500 if it gets at least 5 mpg more. New vehicles must cost no more than $45,000 manufacturer’s suggested retail price. You can get the credit only if you buy a new car, not a used one.

Dealers who choose to participate will be listed online at www.cars.gov, where vehicle owners can also find more information about the program.

Consumers should study the Web site to determine if the vehicle they plan to trade and the vehicle they plan to buy meet all the requirements of the law.