Outdoor Adventure USA

It was once a huge red flag: When a car's odometer would hit 100,000 miles, "it was almost a magic threshold that meant the car was probably worn out," says Kay Wynter, who runs an auto service center in Fort Myers, Fla., with her husband, Terry.

But thanks to improvements in car design and maintenance, the milestone of 100,000 miles now means something very different.

Although some cars are ready for trade-in at that threshold, many others can travel twice as far without major repairs.

What allows one car to pass the 100,000-mile barrier with few repair bills, while another is ready for the junkyard? It's all about preventive medicine.

"It's just like when you get to be 70 and everyone tells you the same thing: Exercise, eat right, take care of yourself," says Lauren Fix, author of "Lauren Fix's Guide to Loving Your Car" (St. Martin's Griffin, 2008).

Feeding your car the right things and taking it for regular checkups will make all the difference.

Open the Book
The key to keeping your car running smoothly is probably tucked at the bottom of your glove compartment, under the spare napkins and ketchup packets. It's the owner's manual, which most people ignore at their peril.

"There is a schedule in the manual that runs well over 100,000 miles," says Fix, and it lists when to replace parts likely to be wearing out. The list will vary for different cars, so check yours and follow it.

Newer cars may have the maintenance schedule built into an internal computer. A blinking light or a beep will announce that it's time to replace certain parts, says autoeducation.com founder Kevin Schappell.

"Things like the water pump and timing belt should be changed before you notice a problem," Schappell says. Replacing them won't be hugely expensive, but "if that belt breaks, it can cause internal damage to the engine, or if the water pump fails, you can overheat the engine and warp the cylinder head."

That's when things get expensive.

"Typically, around 100,000 or 120,000 miles there are some major preventative maintenance things that need to be done," Schappell says, so it's a great time to catch up if you've been lax until now.

Get Fluent about Fluids
The liquids that go into your car (gas, oil, brake fluid, power steering fluid, etc.) are crucial to its survival. To extend the life of your car beyond 100,000 miles, these experts suggest frequent oil changes and fluid checks done at dealerships or full-service auto centers.

The staff at a quick-change lube shop, Fix says, isn't likely to have extensive training. Often, "they don't have experience," she says, "so they'll top off long-life fluid with non-long-life or they'll put power-steering fluid where the brake fluid ought to be."

These mistakes cause damage, but the car owner doesn't realize it until well after the discount oil-change was done.

In choosing oil, Fix advises buying full synthetics. They "actually will lube the engine better. It's designed for longer life. There are less emissions, so it's greener. There's slightly better fuel economy and better performance," she says. "There are no negatives except it costs a little more."

Whichever oil you choose, Schappell says, be consistent over time. That way you won't mix synthetics and blends, which can cause problems.

Gas also matters: Different cars benefit from different types, so check your manual. "For a Honda which runs really hot because of the compression, if it says run premium, then run premium," Fix says. "But if it says there's no benefit from premium gas," you don't need it.

Find the Right Shop
"Do your research," says Terry Wynter, and choose the best people to extend the life of your car. Ask friends and neighbors, and search online for reviews of repair shops.

Once you've chosen one, get to know the staff and ask questions. "Consumers are smarter now than ever before" about their cars, Wynter says, but many still are uncomfortable asking for details about work that needs to be done.

Sticking with your car's dealer can be a safe choice, because the staff will be trained to work on your car. But over the life of a high-mileage car, regular maintenance at a dealership can get pricey.

"Rates at an independent shop may be about $40 to $50 an hour," Schappell says, "but you're paying probably $60 to $90 an hour at a dealer."

The cost of repairs can vary widely depending on the brand of car. Parts for some vehicles, including exotic cars and some German models, can be hard to get, driving up their cost. That can be a reason to trade in a car just before the 100,000-mile threshold.

At 100,000 miles, Fix says, "it is out of warranty and you've got to consider that."

When you do replace parts, there are ways to save money: "A quick oil-change place will charge you $50 for an $18 air filter," she says, because you're mainly paying for labor.

But an auto-parts store will charge you only the $18 price tag, she says, and "you can buy it and say, I don't know how to put this on. They'll do it as a courtesy."

The Type of Miles Matter
It may seem surprising, but highway driving puts less stress on a car that tooling around locally. It requires less quick braking and acceleration, and moisture under the hood has a chance to evaporate.

"Cars that do a lot of short trips will require exhaust work a lot sooner than car that travels on the highway a lot," Schappell says.

Fix agrees: With local driving, "if you sit in rush hour traffic, tow a trailer, idle outside a school, drive on dusty roads, that's considered severe duty."

Local driving in colder climates can also cause buildup of ice and snow under the car, which may contain corrosive chemicals. Fix suggests hosing it off on slightly warmer days. She also suggests waxing your car regularly.

Sound like a lot of work to keep a car zooming along past 100,000 miles?

"It's your second most expensive investment. You want to take care of it," says Fix.

"With your home, something needs fixing and you get on it," she says. "With your car, especially one with a lot of miles you have to get on it right away too."

These small investments will add years to the life of your car.

Willie H wrote:Cool John. Who here is over 100,000 miles? I'm sure it comes much faster for a lot of us since our vehicles are also our toys, and our playgrounds the massice stretches of severe duty land. Which I'll trade the "severe duty" of Fish Creek for the "severe duty" of 5 south afternoon traffic anyday...