Auto lender GMAC Financial Services is getting another $7.5 billion in aid from the federal government.

The Treasury Department says the investment will help provide a reliable source of financing for car dealers and buyers. The company failed its bank "stress test" earlier in the month.

In December, the federal government gave GMAC $5 billion from the $700-billion financial bailout program. In return, the government got 5 million GMAC shares.

Treasury Secretary Timothy Geithner said the loan should help boost the economy.

"This new arrangement with GMAC will help provide a reliable source of financing to both auto dealers and customers seeking to buy cars," Geithner said.