Almost two-thirds of car owners put off automotive maintenance, increasing the chances they will have mechanical breakdowns on the road, according to CarMD.com.

Here's what the automotive repair website says are the most common car problems, according to its database, which uses engine electronic diagnostic reports and other measures to track vehicle failures and repairs.

Replace oxygen sensor: This is the top failure and the most frequent reason for that dreaded "check engine" light to come on. The sensor monitors the amount of unburned oxygen in the exhaust. Failure of what is typically a $20 fan drastically cuts your fuel economy.

Check gas cap: Another culprit behind "check engine" lights is a loose, faulty or cracked gas cap. This also hurts fuel economy by allowing fuel to evaporate, and is an inexpensive repair.

Replace catalytic converter: CarMD says a catalytic converter normally won't fail unless a smaller faulty part, such as a spark plug or an O2 sensor, is ignored for too long.  So if you are maintaining the rest of your vehicle, this shouldn't be a problem. But when it is, it hurts. The repair can cost as much as $2,000. A broken catalytic converter is signaled by a blinking "check engine" light. Pull over and have your car towed if you see that -- before you inflict more damage to your car.

Replace mass air flow sensor: The mass air flow sensor measures the amount of air supplied to your car's engine and determines how much fuel to deliver into the engine. When malfunctioning, it can
result in a lack of power, engine hesitation or a surge when accelerating. The repair can run as much as $300. Replacing the $20 air filter periodically will protect your car from this problem.

Replace spark plug: The plugs or wires can go out, once again killing fuel economy and hurting other systems in the vehicle. Spark plugs usually need to be replaced every 30,000 to 40,000 miles.

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-- Jerry Hirsch
Twitter.com/LATimesJerry

It's a brutal day for stock markets worldwide as Europe's debt crisis worsens and fresh data point to slowing growth in China.

But the U.S. is looking better than most other markets, a sign that Wall Street is viewed as a relative haven -- for now.

The Dow Jones industrial average was down 118 points, or 0.9%, to 12,394 at about 11:50 a.m. PDT. [Updated at 1:20 p.m.: The Dow closed off 130.78 points, or 1.1%, to 12,381.26.)

Nervous money flowed into U.S. Treasury bonds, pushing the 10-year T-note yield down to 3.13% from 3.15% on Friday. Gold also attracted buyers, rising $6.50 to $1,515.30 an ounce in New York.

Europe’s government-debt woes deepened over the weekend after Standard & Poor’s warned that it may downgrade Italy’s credit rating and as Spain’s ruling party suffered a major defeat in nationwide elections.

While most of the focus in Europe this year has been on the heavy debt burdens of Greece, Ireland and Portugal -- all three of which have been bailed out by the European Union -- Italy and Spain are far larger economies, and any thought that they, too, would need debt bailouts strikes terror in financial markets.

With rising expectations that Greece will be unable to pay private bondholders in full despite previous help from the EU, “Europe’s failing approach to its debt crisis has renewed fears of a contagious sovereign default and a possible euro zone breakup, sending shockwaves across capital markets,” said Lena Komileva, a currency strategist at Brown Bros. Harriman in London.

The euro sank 0.7% to $1.406, its lowest since mid-March.

Interest rates jumped on government bonds of Greece, Portugal and Ireland, with the annualized yield  on two-year Greek bonds reaching a record 26.3%, up from 25.5% on Friday, as the market price of the securities continued to sink.

Italian bond yields also rose, but modestly. The yield on two-year Italian notes edged up to 3.07% from 3% on Friday.

The reaction was much worse in the Italian stock market, which plummeted 3.3% to its lowest since mid-January. Stocks also fell 2% in Germany, 2.1% in France and 1.9% in Britain.

Earlier, Asian stock markets had slumped overnight on worries over Europe and after a survey of manufacturing activity in China pointed to a further slowdown in May.

The Shanghai stock market plunged 2.9% to its lowest since early February. China’s slide helped pull the Japanese market down 1.5%%, Hong Kong down 2.1% and India down 1.8%.

The U.S. dollar, the great weakling of global currencies for much of the last nine months, suddenly is back in demand as global investors look for a place to hide. The DXY index of the dollar’s value against six other major currencies is up 0.9% to 76.13, its highest level since March 30.

But that won't be welcomed by American exporters that have benefited from the greenback's slump.

-- Tom Petruno

Photo: On the New York Stock Exchange floor on Monday. Credit: Jin lee / Bloomberg News

Here's your mambo-number-five Monday roundup of consumer news from around the Web:

--Are you being overcharged for your iPhone or iPad? A new lawsuit alleges that AT&T is doing just that, overcharging customers for phantom data transactions. The firm of Thornton, Davis & Fein has filed suit in federal accusing AT&T of overcharging iPhone and iPad customers by as much as 100 kilobytes of data per 50-kilobytes charged. In a test, the firm said an iPhone left unused for 10 days logged 35 data transactions. AT&T says there's nothing fishy going on. The company says there are data transactions running in the background on most smart phones. Just because consumers might not be aware of them, the company says, doesn't mean they aren't needed. In many cases, those transactions may involve apps accessing online data. The class-action suit was filed on behalf of 20 million consumers who own AT&T iPhones and iPads.

--A sweet sign o' the times: Krispy Kreme Doughnuts has reported its biggest quarterly profit in more than seven years, sending its shares soaring. The doughnut chain posted $9.2 million in profit for the first three months of the year, which is a whole lot of sugar going down the gullets of customers. Krispy Kreme has had its work cut out for itself, trying to pitch its glazed confections amid an obesity epidemic and efforts to get people to eat healthier. The company has also faced rising commodity costs, especially for sugar. Krispy Kreme says it is working to offset those costs by reducing the use of some key ingredients and raising various prices. And it appears American consumers have no loss of appetite for the product.

-- David Lazarus

Photo: A lawsuit alleges that AT&T is overbilling for data transactions. Credit: Emmanuel Dunand / AFP/Getty Images

Gold: Trading now at $1,510 per ounce, up 0.1% from Friday. Dow Jones industrial average: Trading now at 12,357.50, down 1.2% from Friday.

European blues. Concerns about the economy in southern Europe are making for another bruising day in the markets.

IPO inflation. After last week's frenzied pursuit of LinkedIn shares, investors appear to think the euphoria went too far and are sending shares down Monday morning. Meanwhile, a debate rages about whether LinkedIn's bankers wronged the company by not seeing how much the stock would rise after the initial offering.

Tricky traders. The Wall Street Journal's analysis showed that Los Angeles County's pension fund was regularly given the short end of the stick by its bankers when it needed to do currency trades.

Utah gold rush. Utah is appealing to gold bugs, and bringing back a small piece of the gold standard, by legalizing gold coins as legal currency.

-- Nathaniel Popper in New York

Photo credit: National Geographic

The long-awaited moment of relief for U.S. motorists might finally be at hand. The drop in retail gasoline prices has finally gained momentum with the California average falling by nearly a dime in the past week and the U.S. price declining by more than 11 cents.

It was fast enough for one analyst to reiterate his opinion that the state's prices were heading toward the $3.50 to $3.75 a gallon range in the coming weeks. But the analyst, Tom Kloza, now says it should be closer to $3.50 a gallon in California.

He added that the sharp drop should stoke  concerns that the dramatic rise in fuel prices that began last September was driven more by Wall Street speculation, not by supply and demand influences. Gasoline supplies were ample through much of the biggest price jump since the summer of 2008.

"If anything, I think a lot of us are surprised that the pace hasn't quickened a bit more. There was so much speculative investment money bet on crude oil and on gasoline that it had to fall," said Kloza, chief oil analyst for the Oil Price Information Service.

"For those of us who have watched a long time, this was a combination of hysteria and euphoria for the speculators. You had the panic mentality of the crowd who collectively acted like blockheads," Kloza said.

In California, the average price of a gallon of regular gasoline reached $4.118, down from $4.217 a week earlier, according to the AAA Fuel Gauge Report. The AAA uses receipts compiled daily at more than 100,000 retail outlets across the U.S. by the Oil Price Information Service and Wright Express.

Discount gasoline chains were clearly leading the charge. At Costcos, Sam's Clubs, and Food 4 Less stations in many parts of Southern California, a gallon of regular gasoline could be bought for as little as $3.84 to $3.88.

Nationally, the AAA Fuel Report said that the average cost of a gallon of regular fell to $3.843, down from $3.955 a week earlier, as the worst Mississippi River flooding in more than 70 years failed to have a major impact on several large refineries.

Investment planner Jacob Gold of Jacob Gold & Associates Inc. cited quick thinking from the Army Corps of Engineers in opening spillways on the river.

"The Mississippi River may have crested in New Orleans late Saturday.  By opening a spillway upriver nine days ago, the river's level reached only 17 feet or 2 ½ feet lower than what would have occurred had the spillway not been used. The levees in New Orleans are 20 feet high," Gold said.

Oil continued to fall as well on Monday. Crude oil futures had dropped by more than $3.50 a barrel to $96.50 a barrel in trading on the New York Mercantile Exchange. London's Brent crude futures fell more than $3.80 to an intraday low of $108.58 a barrel.

--Ronald D. White

‘Free’ trial offers -- The Federal Trade Commission has accused an Alberta, Canada, man and several companies of defrauding consumers of more than $450 million  by luring them into “free” trial offers and then charging them for products or services they did not order. The FTC filed a lawsuit in the federal courthouse in Seattle against Jesse Willms and 10 of his companies, accusing them of obtaining victims’ credit card numbers as part of free-trial offers and then billing the credit cards for products that were not ordered. Consumers from the United States, Canada, Britain, Australia and New Zealand were victimized in the scam, the FTC said in a news release. The lawsuit seeks an injunction prohibiting the companies from engaging in similar practices and an order freezing their assets, as well as restitution for victims.

Pre-IPO schemes -- Investors should be careful when responding to opportunities to buy pre-initial public offering shares of Facebook, Twitter, Groupon or other popular companies, the Securities and Exchange Commission said in a recent alert. A number of these unsolicited offerings are scams that have been promoted through social media, the Internet, telephone and email, the SEC said. Investors should be wary of the risks of such investments and carefully research the investment product and the professional making the offering, the SEC said.

Movers -- Consumers should be careful when selecting a professional mover, the Better Business Bureau said in a recent bulletin. The BBB received more than 8,900 complaints about dishonest and unlicensed movers last year. Most of the complaints alleged that the movers charged more than original estimates or that they lost or damaged property. In some instances, dishonest movers hold consumers’ belongings “hostage” until they are paid thousands of dollars, the BBB said. To avoid such problems, consumers should research companies thoroughly and get in-person estimates, the BBB said.

Guaranteed returns -- The SEC is warning consumers to avoid investment offerings from a company called Imperia Invest IBC, which the agency said has fraudulently raised more than $7 million from investors worldwide. The SEC alleged in a lawsuit that the company guaranteed on the Internet that it would provide 1.2% daily returns but has not paid any returns to consumers. More than half the funds were collected from U.S. investors who are deaf, the SEC said. The agency cautioned that investment pitches guaranteeing spectacular rates of return are an indicator of possible fraud.

-- Stuart Pfeifer

-- It's been a busy week for the nation's most well-known bookstore chains. On Thursday, Barnes & Noble announced that it had received a buyout offer from Liberty Media for $17 a share in cash. And Borders is reportedly in talks with a potential bidder; a deal would help keep the company, which filed for Chapter 11 bankruptcy protection in February, operating as a going concern.

-- Mall owner Westfield will offer its Westfield Family program for the third year. The free membership program is offered at 30 shopping centers around the country and includes family-friendly activities, events, promotions and amenities. New this year to the program are Westfield Family Fun Days, two free activities a month geared toward children ages 2 to 5 and their parents.

-- Lands' End wants to help boost women's self-confidence as summer approaches. The apparel retailer is launching a National Swimsuit Confidence Week starting Monday. The company says the movement was created to "celebrate women of all shapes and sizes as well as educate and inspire them to embrace their swimsuit beauty." Lands' End has partnered with Curvy Girl Guide to kick off the campaign. On Monday, 21 Curvy Girl writers will pose in their Lands' End swimsuit and post the photos on Facebook.

-- Andrea Chang

LinkedIn Corp.'s shares closed slightly lower Friday, one day after the professional-networking firm's spectacular market debut.

The stock lost $1.16, or 1.2%, to $93.09 after rocketing 109% on Thursday from its initial public offering price of $45.

The trading pattern Friday looked similar to Thursday: The stock rose early in the session, reaching a high of $107, then drifted lower the rest of the day.

Volume calmed down considerably: 8.56 million shares changed hands, down from 30.1 million on Thursday. With just 7.8 million shares sold in the IPO, some portion of the stock was flipped multiple times the last two days. That’s typical of a hot new issue, if not exactly heartening to anyone trying to be a long-term investor.

At Friday’s closing price the stock was trading at 547 times the 17 cents a share LinkedIn earned last year on $243 million in sales. (See the detailed prospectus for the IPO here.)

Investors in LinkedIn obviously know they have a highly valued stock. A lofty price-to-earnings ratio has never been an obstacle when the market believes it has found the Next Big Thing -- which clearly is how Wall Street is treating social networking.

Plus, with LinkedIn warning that it won’t be profitable this year because it plans to spend aggressively to expand its franchise, investors aren’t going to be focused on the bottom line, anyway. More likely, the stock’s price trend in the near term will be determined by what LinkedIn can show in quarterly revenue growth.

It will be interesting to see how far out on a limb Wall Street analysts will go in projecting the stock's potential, once research reports begin to roll out in the next few months.

On Thursday, independent researcher Morningstar Inc. took a stab at estimating "fair value" for LinkedIn's shares based on the company's prospects, and came up with a number that won't make any  current shareholder happy: $27. And that "assumes LinkedIn extends its dominance as the preferred social-networking site for professionals," Morningstar said.

LinkedIn’s stock market value now is $8.8 billion. That’s a fraction of Google Inc.’s market value of $169 billion, and it’s a lot less than the market values of Yahoo Inc. ($21.2 billion), Juniper Networks ($20.7 billion) and Netflix Inc. ($12.9 billion), to name just a few other Internet plays.

But at $8.8 billion LinkedIn is worth more than many much older non-tech brand names, including Harley-Davidson ($8.6 billion), Textron Inc. ($6.3 billion) and Whirlpool Corp. ($6.2 billion).

-- Tom Petruno

As the nation's baby boomers sign up for Medicare, they face a bewildering assortment of questions about their healthcare.

In addition to a raft of complicated information from the government, a national consumer group also is offering some answers.

Consumers Union, the nonprofit publisher of Consumer Reports, has produced a free guide about changes this year to the federal government's insurance program for the elderly under the new national healthcare law.

The 16-page manual, "Medicare: 6 things you need to know now," is aimed at the 36 million Americans covered by the original Medicare program and 11 million others enrolled in private Medicare Advantage plans.

It lists, for example, the many preventive medical services that are fully covered under the law for those in the original Medicare program. These include prostate and colon cancer screenings, mammograms, flu shots and pneumonia vaccinations.

The guide also explains how prescription drug costs will decrease once Medicare beneficiaries reach the so-called doughnut hole -- the point in Medicare drug plans at which beneficiaries have paid the full amount in the past for medications.

"Whether you have Medicare, you're about to be eligible, or have a loved one in the program, the guide helps you sort through what's new in today's system," said Jim Guest, president of Consumers Union.

The guide can be downloaded at http://www.consumerreports.org/health/insurance/one-year-health-reform-guide-5-11/index.htm. A Spanish version is available at espanol.ConsumerReports.org/salud.

Copies also can be obtained by calling 1-855-CR-GUIDE.

-- Duke Helfand

Here's your feel-the-burn Friday roundup of consumer news from around the Web:

-- From the you're-not-alone file: About 40% of Americans say high gas prices are having a significant effect on their bottom lines. A poll by the Associated Press finds that 71% of drivers say rising prices will cause some hardship for them and their families, including 41% who called it a "serious" hardship. On the other side, 29% said rising prices are not having a negative effect on their finances. Things are especially tough for senior citizens. The share of seniors with financial hardship over gas prices hit 76%. That number is up from 68% in March. Some say they're even giving up expensive medicine to stay on budget. Of drivers making changes to deal with the rising gas prices, 72% say they're cutting back on expenses, 66% say they're driving less and 48% say they've changed their vacation plans. Southern California gas prices top $4 a gallon in all counties.

-- Wall Street is happy about a buyout offer for bookseller Barnes & Noble. Shares in the company jumped sharply higher after John Malone's Liberty Media offered to buy it for about $1 billion. Being part of a bigger conglomerate could boost Barnes & Noble's ability to invest in remaking itself for the age of electronic books, analysts say. The offer values Barnes & Noble shares 21% higher than their Thursday closing price of $14.11. Barnes & Noble has 705 stores nationwide and 636 bookstores run by its Barnes & Noble College Booksellers subsidiary. The company put itself up for sale in August in response to pressure from billionaire activist shareholder Ron Burkle.

-- Heads up: Honda is recalling about 1,150 Civics from the 2012 model year due to a potential problem with the fuel line, which could potentially spring a leak. "During manufacture of the fuel line assembly, an O-ring may have been displaced, which could potentially lead to a fuel leak at a joint where two segments of pipe attach to each other," Honda says. Most of the cars affected by the problem have not been sold yet and dealers will repair them before they leave the lot. Honda says there have been no reports of injuries or fires related to the fuel feed line problem.

-- David Lazarus

Photo: High gas prices are hitting people in the pocketbook. Credit: Bruce Halmo / Associated Press

Gold: Trading now at $1,511 per ounce, up 1.3% from Thursday. Dow Jones industrial average: Trading now at 12524.80, down 0.6% from Thursday.

Big fraud investigation. A Huffington Post scoop earlier in the week about a fraud investigation of five giant banks is attracting more attention as the week goes on.

Betting on B&N. Fresh off its success in turning around Sirius XM satellite radio, Liberty Media last night made a  bold $1-billion bid to buy Barnes & Noble.

Hedge fund folds. One of the biggest hedge funds to come under scrutiny in the government's insider trading probe, FrontPoint Partners, appeared as though it would survive but is now throwing in the towel.

Joining the quants. SAC Capital, an old-school stock-picking hedge fund, is joining the rush toward computer-based algorithmic trading.

--Nathaniel Popper

Credit: Getty Images/Stan Honda.