NEW YORK (CNNMoney.com) -- The results from Cash for Clunkers are in: Compact cars and hybrids were top sellers under the government's trade-in program, according to government data.
The top-selling car in the Cash for Clunkers program has been the Ford Focus.
The top-selling car was the Ford Focus, and the top three -- including the Honda Civic and Toyota Corolla -- were compacts. The list also includes three vehicles that are available as hybrids. One, the Ford Escape, is a small crossover SUV also available as a hybrid.
The list indicates that consumers are buying more fuel-efficient vehicles than most people expected.
The average combined city and highway fuel economy of the 10 cars ranges from 27 to 33 miles per gallon, depending on which versions people choose.
Under the plan as enacted, vehicles purchased after July 1 are eligible for refund vouchers worth $3,500 to $4,500 on traded-in gas guzzlers. The trade-in vehicle has to get a combined city and highway fuel economy rating of 18 miles per gallon or less.
The list was compiled by the National Transportation Safety Administration, which operates the program.
The news of the top sellers comes as the debate is heating up in the Senate over whether to extend funding for the program. Some lawmakers have argued that the rules for the program aren't strict enough when it comes to fuel economy.
While critics had feared that car shoppers would use the program mostly to buy trucks, 83 percent of the vehicles traded in have been trucks and SUVs while 60 percent of vehicles purchased were passenger cars, according to Secretary of Transportation Ray LaHood. Watch what will happen to "clunkers" traded in »
The broad category of SUVs includes many small car-like crossover SUVs, including the Escape, which get much better fuel economy than large, truck-based vehicles.
Last month, many of the vehicles with the biggest reported year-over-year sales gains were small crossovers, a fact that several of the top automakers attributed to the Cash for Clunkers program.
The average fuel economy of new vehicles being purchased under Cash for Clunkers is 25.4 mpg, LaHood said, and the average fuel economy increase from the old vehicle to the new is about 61 percent.
"It's crazy, but we're seeing trucks -- full-size pick-up trucks -- traded in for compact cars," said Mike Jackson, chief executive of AutoNation, the country's largest auto dealer chain, in interview late last week.
The popular Clunkers program faces extinction unless the Senate passes a bill approving additional funding.
The House on Friday passed a bill authorizing an additional $2 billion for the program after it burned through its original $1 billion budget.
And on Tuesday, it appeared likely that the Senate will vote for the funding before it breaks for summer recess on Friday.
"We'll pass Cash for Clunkers ... before we leave here," said Senate Majority Leader Harry Reid, D-Nevada.
Even senators who have been critical of the program conceded they can't stop it.
"In the end, we know where the numbers are," acknowledged the third-ranking Senate Republican, Sen. John Thune, South Dakota, who said he expects all Democrats and several Republicans to vote for additional funding.
For his part, LaHood said he was confident the Senate would approve the additional funds.
"We are not discontinuing the program," LaHood said.
CNN's Ted Barrett and Jeremy Harlan contributed to this report.