Never let it be said US car buyers don't know a good deal when they see one. The Toyota Prius has become the fourth-most popular car purchased under the first 80,000 Cash-for-Clunkers vouchers processed by the US Department of Transportation.

In fact, Toyota sold 19,173 Priuses during July, almost 30 percent more than a year ago and a full 41 percent higher than the total sold in June 2008.

The Prius is the only hybrid in the ten most popular vehicles purchased under the Car Allowance Rebate Systems (CARS) program, colloquially called "Cash for Clunkers."

In fact, the Cash-for-Clunkers program has been so popular that it may run out of funds less than two weeks after it launched. The US House of Representatives voted Friday to transfer $2 billion to the program from energy-loan guarantee funds, and the Senate will consider whether to support the extension before it recesses at the end of the week.

Required: 22 mpg or more for cars

Under the program, owners of 1984-2002 vehicles with a combined EPA mileage rating of 18 miles per gallon or less qualified for a $3,500 voucher towards the purchase of a new car rated at 22 mpg or better. The maximum voucher of $4,500 was available to those who bought cars rated at 10 mpg (or more) higher than the trade-in.

There's a different scheme for trucks: The new vehicle must be rated at 18 mpg or better, and it also has to be 2 mpg more efficient than the truck traded in to qualify for a $3,500 voucher. Boosting the mileage by 5 mpg or more gets you the full $4,500.

The 2010 Toyota Prius, with its combined EPA mileage rating of 50 miles per gallon, is by far the most fuel efficient car available under the Clunkers program.

And the program has clearly worked as intended, with the new vehicles purchased using Clunker rebates averaging almost 10 miles per gallon more than the vehicles traded in.

The bulk of vehicles traded in were light trucks, both sport utility vehicles and minivans. Those purchased, on the other hand, were largely compact and midsize sedans and hatchbacks.

2010 toyota prius first drive 002

2010 toyota prius first drive 002