The Great Car Maintenance Upsell

Got a tale of an overzealous repairman? You're not alone. With the recession crimping profits, repair shops are under growing pressure to sell extra services that critics say probably aren't necessary -- everything from "decarbonization" to transmission fluid "flushes" that, at the end of the day, can inflate your bill by hundreds of dollars.

The sales push is happening because drivers aren't just putting off new-car purchases; they're also scaling back on service appointments. According to market-research firm IMR, the $133 billion car-repair and maintenance industry saw declines last year in almost every category, with basic maintenance down almost 10 percent. To make up for lost revenue, the greasy-overalls brigade is scrambling. "They're pushing to do things earlier and more frequently," says Philip Reed, an auto-repair expert with Edmunds.com.

Ask Ken Massey. A veteran grease monkey who has worked on his own vehicles since the days when tail fins ruled the road, he was a bit leery when he stopped by a local car dealer to replace a blown fuse in his Chevy Cavalier and was told that, by the way, his transmission had sprung a leak. Fix it on the spot, the "service adviser" urged, and it would cost only $325. But Massey, a retired engineer in Indianapolis, wasn't buying it; the transmission had no leak he could see. "I think they got a little greedy," he says.

Of course, shops that go too far in upselling services risk a backlash and loss of business. They lose their AAA seal of approval, for example, if they don't score above 90 percent on annual customer-satisfaction surveys. But with car upkeep these days requiring technicians to get advanced training in computers and electronics, even dedicated gearheads have trouble staying current enough to know whether they're being overserviced.

In an era when your shop may charge you $100 just to plug the car into a diagnostic machine to learn why the "check engine" light came on, we looked into the science of auto maintenance.

The Tune-Up

In the old days, cars used to need an oil change and maintenance check every 3,000 miles. But parts are now built to last longer, says James Grey, president of AAA Car Care, and it's usually not necessary to get your car checked as frequently. Still, many garages promote seasonal tune-up packages that include dozens of extraneous items -- think wiper blades, timing belts and coolant mix. Says Grey, "The industry has designed maintenance schedules according to its needs instead of car owners'."

That oil change? Turns out every 5,000 miles is often enough. New oil has chemicals that eat away the catalytic converter, says Donny Seyfer, a Colorado-based certified master technician, and changing oil too often can damage that pricey part.

Another common upsell is to recommend "turning" the brake rotors when you get a new set of brake pads. But unless the rotors are visibly damaged, owners should skip it, says Reed of Edmunds.com, since the process involves shaving off metal and could ultimately reduce their performance and lifespan. Still, experts say, sometimes being proactive -- changing your brake pads before the rotors are damaged -- can prevent an expensive brake overhaul further down the road.

Engine & Transmission Maintenance

When Ryan Endres of Madison, Wis., saw the "check engine" light flash in his 2000 Isuzu Amigo, he figured it might be a cracked intake manifold, a recurring problem with his SUV. In reality, so much sludge had built up in the engine that he needed it "decarbonized," a process that cleans the intake valves with a solvent.

While it was the right fix for his car, decarbonization is being pitched by more shops to generally boost performance and mileage. But critics say the gains are minimal, and even carmakers don't recommend it as a routine service item. "Unless the vehicle has over 150,000 miles, it's probably unnecessary," says Andrew Markel, a repair-industry specialist.

Another popular pitch: fluid flushes. Shops may tell you your transmission fluid needs replacing, more frequently than manufacturers suggest. Aamco for one, recommends its "Power Purge" flush every 24,000 miles, but Ford doesn't advise it for any of its models, and Toyota recently urged its dealers to scale back on such "supplemental" services. An Aamco spokesperson acknowledges that its fluid-change intervals aren't the same as manufacturers' but says that its time frame "will maximize the life of the transmission."

Tires

Tires might seem like the last thing you'd want to skimp on -- a blowout, after all, can be deadly. But all tires have to meet the same federal safety standards, and drivers can save big bucks with a second-tier brand. Goodyear, for instance, has two "associate" lines -- Republic and Fierce -- that are essentially Goodyear tires with hand-me-down technology. True, says Goodyear spokesperson Jim Davis, they aren't constructed with the "latest and greatest" features, like Kevlar lining (the material used in body armor) and "volcanic sand" (for grittier traction). Still, they can cost up to 50 percent less.

Tiremakers have just begun promoting new "low-rolling-resistance" models they say can save fuel. Michelin says its Energy Saver All-Season tire, though pricier than other tires, delivers 8 percent better gas mileage.

Whichever tires you use, don't get sucked into filling them up with nitrogen -- an increasingly common practice -- instead of air (cost: up to $3 per tire). Though some studies suggest it helps tires last longer, the carmakers don't recommend it. "What will it do for your tires?" asks Grey. "Nothing."