Prevention by the quart beats cure by the bank account

Remember, you've spent a bundle for your car. New passenger vehicles sold for an average price of $27,751 in Virginia in 2011, according to the state Department of Motor Vehicles.

And it's going to be on the road for a decade or more. The average passenger vehicle registered in the state was 10.2 years old last year, the DMV said.

People are holding on to cars longer because of the recession, experts say, and cars can last longer because they're better built than a generation ago.

But they still need some critical TLC, for safety's sake and to keep the car running at top efficiency.

Beyond that, regular maintenance checkups can help forestall spending big bucks to fix major problems down the road.

Changing the oil is key

Changing the engine's motor oil "is the single most important thing you can do to make your engine last," said Lawrence "Kelly" Schwendeman, head of J. Sargeant Reynolds Community College's automotive technology program.

Oil lubricates, protects, cleans and cools the many hot moving parts that make up the engine, which in turn makes your car go — and costs a lot of money to fix when it won't.

As oil is continually heated and cooled and heated and cooled again as the engine operates, its lubricating qualities gradually break down.

Without enough clean oil, engines will wear more rapidly and could even seize and be destroyed, AAA cautions. And a new engine can be a $5,000 investment, Schwendeman said, and even a used engine can cost $2,500 installed.

Meanwhile, a quart of motor oil runs about $4 to $5 for commonly available, reputable brands.

"Certain things are very cheap and clearly serve you very well," said auto industry expert George E. Hoffer, a transportation economist at the University of Richmond, "and that's changing your oil."

Trying to skimp on oil changes is counterproductive, Hoffer said. "The marginal cost to you of something happening is much greater than the margin benefit you get" from trying to stretch the oil's life.

Follow the manual

"You need to go by the owner's manual, not old wives' tales," said Schwendeman.

"They all have maintenance schedules in there. Try to stick to it, and you won't have unscheduled, premature failures," he said. "You'll save yourself money in the long run."

Following the car's recommended maintenance plan is critical for vehicles under warranty, because if you don't and there's a warranty claim, it might not be covered, said David Wright, manager of AAA Mid-Atlantic's approved auto repair program.

And, Wright said, "Every car on the road, you can download a free owner's manual for it by going to the manufacturer's website."

Check tires

"One of the best things you can do is check the tire pressure," Wright said.

Cars are designed to run on a specific tire pressure, said Schwendeman, from J. Sargeant Reynolds. "Too high or low causes abnormal tire wear, and the handling characteristics may be unsafe."

Tires can lose a pound per square inch of air pressure every couple of weeks, experts say. That in turn will cut into the car's mileage.

Underinflated tires can lower gas mileage by 0.3 percent for every 1 pound per square inch drop in pressure of the tires, according to the U.S. Department of Energy.

As seasons change, tires lose or gain another pound of inflation pressure for every 10-degree change in outside temperature.

When a tire's inflation is low, "it's basically slapping the road rather than rotating," Schwendeman said. That heats the tire and can cause it to come apart.

If underinflation isn't good, neither is overinflation, which lifts the outer edge of the tread off the road, wearing the tread unevenly, and again overheating the tire and producing tire failure.

AAA suggests checking tire pressures at least once a month, when the tires are cold. And don't use the inflation pressure molded into the tire sidewall: It might not be the correct pressure for your particular car. Use the pressure called for in the owner's manual.

Grip the road

Tires keep your car connected to the road — and under control.

When roads are wet or snowy, having tires with enough tread to grip the highway is crucial.

"Worn tires with inadequate tread are much more likely to hydroplane on wet pavement or lose traction in the snow," AAA pointed out, "resulting in a loss of braking power and steering control."

As a rule of thumb, the travel group said, you can check your tires by inserting a quarter on its edge into a tread groove: "If you can see above Washington's head at any point, replace the tire."

Tire troubles are predictable, Hoffer said, with 90 percent of problems occurring in the last 10 percent of a tire's life.

And when tires fail, they go with a bang: "What do you save from trying to get a little bit more out of it?"

Replace them before they blow out, he suggests, noting that it also pays to buy better tires: "They'll last longer and ride significantly quieter."

Spark of life

Power from the battery flows to your vehicle's electrical system through cables, clamps and terminals.

If those are corroded or loose, your car won't get the power needed to start the engine and run other systems.

Motorists should have the battery cables and connections inspected when they do their regular oil changes.

If your battery is more than 5 years old, change that, too, Hoffer said. "It's risky business, especially in the dead of winter or the height of summer."

"If you get one more year out of it, you save $10," he said. "What is it going to cost you when the battery fails — and it will fail unexpectedly. Will it cost you a day's work? Will you be in a compromising place?