Americans increased credit-card use for the first time since 2008, a sign they are growing more confident about the economy and opening their wallets wider.

The surprising rise in December revolving credit as tracked by the Federal Reserve pushed up consumer credit outstanding by $6.1 billion, or 3.0 percent, to $2.41 trillion. Economists surveyed by Dow Jones Newswires had forecast the Fed data Monday would show consumer credit rising by only $2.5 billion.

The Fed also revised up November consumer credit, saying it rose $2.0 billion instead of $1.3 billion as originally reported. Consumer borrowing also rose in October.

The three straight increases add to evidence the economy is gaining traction against such headwinds as an ailing housing sector and high joblessness.

Consumer spending is a big part of the economy. Rising spending at the end of 2010 made the economy grow faster. Last week, the government said spending accelerated in December as wages and salaries grew and inflation stayed mild. The savings rate eased, a signal Americans are growing more comfortable with the recovery. An extension of federal income-tax cuts is letting consumers keep more of their paychecks, which should help support spending going forward.

The report Monday on December consumer borrowing showed revolving credit, or credit-card use, rose $2.3 billion, or 3.5 percent, to $800.5 billion. The last time credit-card debt had gone up was in August 2008, a month before investment bank Lehman Brothers filed for bankruptcy and brought turbulence to financial markets.

Nonrevolving credit also climbed in December, by $3.8 billion, or 2.8 percent, to $1.61 trillion. The category includes loans for cars, mobile homes, tuition and other things.

The consumer-credit report doesn’t include numbers on home mortgages and other real estate-secured loans. But the data are important for the insight given into consumer behavior.