Avoid a warranty 'void'

Last month's surprising surge in new-car sales – up nearly 3 percent overall after an also-strong March – put the industry on a pace to sell 17 million new vehicles by year's end.

With each of those gleaming sets of wheels comes a warranty, a manufacturer's promise to stand behind the quality of its product.

But as with any contract, warranties are subject to interpretation. One result: the possibility of loopholes that manufacturers or dealers can use to get out of paying for repairs.

For carmakers, warranties are all about keeping buyers happy while weeding out fraud, says David Cole, director of the Center for Automotive Research at the University of Michigan, Ann Arbor.

With the length of manufacturer warranties growing – 100,000 miles for Hyundais and Kias and 120,000 miles for most Isuzus – claims can quickly run into the billions of dollars. So automakers may have more reason to fend off consumer claims that – multiplied by scores of thousands of vehicles – can quickly run into the billions of dollars.

What can consumers do to make sure their warranties hold up?

Rule No. 1: Read and follow your owner's manual.

Most manuals now specify that oil should be changed every 7,000 miles for "ordinary use." But they insist that under "severe" or "extreme" driving conditions, the oil be changed more often – every 3,000 to 5,000 miles.

"If you read the fine print in the owner's manual, most normal driving is defined as severe," says Mike Allen, auto-repair expert with Popular Mechanics.

For example, here's what a recent Chrysler owner's manual defines as "extreme" use: "... if you drive mostly short distances, operate the vehicle in dusty areas or under predominately stop-and-go traffic conditions, or [live] where temperatures remain below freezing for extended periods."

A similar clause recently gave Toyota room to say owners didn't change their oil frequently enough. Earlier this year, Toyota faced hundreds of claims that its most popular engines seized after the oil turned to sludge. The company initially balked at the claims, blaming owners for failing to change their oil often enough. But after some owners threatened legal action, Toyota agreed to cover the repairs, and instituted design changes to eliminate the problem in new engines.

Rule No. 2: Keep receipts for all routine maintenance.

Jobs not normally covered by warranties, such as oil changes and brake jobs, need not be done by dealers. A series of lawsuits in the 1980s established that consumers who use independent garages retain the right to coverage.

Still, having a dealer perform maintenance scheduled in the owner's manual until the warranty expires can make sense. "Basically, the more you don't take it to dealer, the more trouble you're going to have defending a warranty claim," says David Champion, head of auto testing at Consumer Reports. Only four major service intervals (every 7,500 miles) occur before most warranties expire, he notes. So the expense is minimal to make sure all the recommended work is done.

Rule No. 3: Use factory parts – at least until the warranty expires.

While the law allows you to install, say, a replacement oil filter, the manufacturer may not honor a warranty claim if it considers that filter an inferior product.

Modifications to your car are more problematic. For example, aftermarket brake-dust guards sold in high-end catalogs may cause brakes to overheat, and void warranty claims on the brakes.

Experts agree that aftermarket modifications that don't meet original specifications – even changes as simple as bigger wheels – can void a warranty. But they only affect the specific systems modified. So, for instance, new wheels and tires could void the factory warranty on suspension parts. But a muffler would still be covered if it rusts through.

Auto experts offer advice on how using certain products and services might affect a new car's warranty. They include:

• Synthetic oil. This nonpetroleum product has come a long way in the past 10 years. There's no longer any reason not to use it, except that it costs twice as much as regular oil, says Howie Ferris, director of applied technology at Massachusetts Bay Community College in Wellesley, Mass. Most auto warranties now accept synthetic oil such as Mobil 1.

• Regular versus premium fuel. While some owner's manuals require premium, using regular unleaded shouldn't void a car's warranty, experts say. Modern cars contain sophisticated electronics to gauge and eliminate knocks and pinging even without premium fuel.

• Rustproofing. Aftermarket rustproofing can void a manufacturer's rust-through warranty, since it often plugs holes designed to drain water out of a car's body. Most of today's cars use modern materials and technology to prevent rust, and have corrosion warranties that last up to 12 years. It's unlikely any rustproofer's warranty would outlast that.

• Trailer hitches. While these items shouldn't void a warranty, a hitch with a "weight class" exceeding the maximum towing capacity of the vehicle may tempt you to tow more weight than you should, putting stress on other components. Also, note that the manufacturer's rating usually assumes installment of the manufacturer's optional towing package.

The length and breadth of manufacturer warranties vary widely from make to make. All new vehicles come with three types: basic, drivetrain, and corrosion. Basic covers everything except items subject to wear and tear. Drivetrain covers most parts that make the car move, such as the engine and transmission. Corrosion guarantees that a vehicle will not rust through for certain time periods, usually five or six years. Most manufacturers also offer some roadside assistance. Assistance guarantees most often run three years or 36,000 miles, whichever comes first. Mercedes has the best package, with no limits imposed on their cars' age or mileage. When it comes to basic warranties, the most extensive are offered by Korean carmakers. The least extensive come with most American models. Japanese and European makes fall somewhere in between. Below is a list of which manufacturers offer the longest basic warranty, along with information about drivetrain coverage.