One afternoon a few months ago, Seattle resident Don Clifton drove his white pickup truck—a 2007 Ford Ranger—to a Jiffy Lube in Ballard. An attendant in coveralls asked him what he wanted. He said he wanted his oil changed. "Do you know how your air filter is doing?" the attendant asked. "Should we top off the coolant? Are any of your lights out? Windshield wipers okay for you?" Clifton said he just wanted his oil changed.

The attendant got in the driver's seat, slapped a plastic wrapper over the steering wheel—to keep off the motor grease—and eased Clifton's truck into the garage until the underbelly of its chassis hung above a subterranean mechanics' pit. Clifton went to a nearby cafe and ate a sandwich. When he returned, the attendants put a little sticker on the inside of his windshield—the same little sticker all 24 million customers of Jiffy Lube get on the inside of their windshields each year—telling him to come back for another oil change after 3,000 miles. Clifton showed me the owner's manual with the guidelines that Ford—the people who designed and built his engine—suggests for changing the oil: once every 5,000 miles. (That's relatively low for a new car—some major manufacturers recommend changes at 7,500- or 10,000-mile intervals.)

"See, that's just wasteful," he said. Think of how much money, time, and oil Americans could save if they just followed manufacturers' guidelines instead of Jiffy Lube's misleading recommendations. A little laziness, he said, could make the world a better place.

Jiffy Lube, which is a subsidiary of Shell Oil, has more than 2,000 franchises and 24 million customers. The US Department of Transportation says the average American driver covers 13,476 miles of pavement a year. Every oil change takes about five quarts of oil. That's 4.49 oil changes per year x 5 quarts of oil x 24 million customers, which equals 134,760,000 gallons. If Jiffy Lube customers got their oil changed half as often, they could save more than 67,380,000 gallons of motor oil per year.

Incidentally, one barrel—42 gallons—of crude oil is involved in making two quarts of motor oil. Other petroleum products are refined from that barrel as well, but each five-quart oil change has been extracted from 105 gallons of crude. The 67,380,000 gallons of motor oil Jiffy Lube customers don't need to buy each year are gleaned from more than one billion gallons of crude oil. The unnecessary oil consumption of Jiffy Lube customers is a drop in America's oil bucket. But it's a 67-million-gallon drop.

It was only this summer—after years of lobbying against the 3,000-mile myth by General Motors, the government of California, and others—that Jiffy Lube announced it would switch its recommendations from a flat 3,000 miles to manufacturer guidelines.

Americans change their oil too often. Craig Linington, director of operations at Jiffy Lube, said that as of early November, customers were changing their oil at an average interval of 3,517 miles if they thought they drove in "severe" conditions. (In a June story for USA Today, Jiffy Lube CEO Stu Crum said 47 percent of his customers thought they drove in "severe" conditions.)

An informal poll of 20 car owners at The Stranger showed that the majority changed their oil every 3,000 miles—not just because of the quick-oil industry, but because of antiquated wisdom. "My dad always told me to change the oil every 3,000 miles, so I did," someone said about her 2002 Honda Civic. Honda recommends a 10,000-mile interval.

For decades, car manufacturers have recommended that people get their oil changed every 5,000 to 10,000 miles. Popular experts recommend similar intervals. Tom and Ray Magliozzi of NPR's Car Talk say, "For the vast majority, 5,000-mile oil changes will help your engine last to a ripe old age." The experts at Edmunds.com say the average recommended interval for cars made in 2010 is 7,800 miles.

Despite Jiffy Lube's official switch, not much has changed on the ground. Jiffy Lube erected computer kiosks in its stores, which supposedly give accurate manufacturer recommendations based on whether customers drive in "severe" or "regular" conditions. (Drivers in "severe" conditions—half of Jiffy Lube's customers, according to CEO Crum—get the 3,000-mile recommendation.)

According to Jiffy Lube's website and employees contacted for this story, any of these driving conditions counts as "severe," warranting a 3,000-mile oil change: stop-and-go traffic (city driving), prolonged speeds (highway driving), short trips (suburban driving), and driving anywhere that's hot or cold or dusty or muddy or hilly.

"It's hard for us to find anyone who drives in normal conditions in the United States," said one Jiffy Lube employee at a Kirkland shop. "They have what they call 'severe driving conditions,' said an employee in Gig Harbor, "which is silly because everybody drives in that category."

Last week, I called 77 Jiffy Lube locations in the Seattle area to test Jiffy Lube's supposed abandonment of the 3,000-mile rule. I alternated hypothetical cars, asking mechanics how often I should change the oil in a 1997 Volkswagen Golf or a 2002 Honda Civic. (The manufacturers of both cars recommend an oil change every 10,000 miles.)

Thirty-five shops unequivocally recommended the 3,000-mile change. Nineteen said some variation of it depends, but you probably want to go with 3,000 miles. ("Jiffy Lube says 3,000, but it's up to you guys now," said one unusually permissive mechanic in Federal Way. "It's your car, so you can do whatever you want.") Seventeen consulted with the kiosk, all promising their computers had accurate manufacturer guidelines. All of them lowballed the manufacturer's recommended interval. Only two said I should stick to my manufacturer guidelines.

"You never, ever want to go over 3,000," said one mechanic in Everett. "After 3,000, it just breaks down completely." That is another fearmongering untruth: Ryan Stark of Blackstone Labs, who has been a motor-oil expert since 1997, says oil-thin engines give warning signs before completely breaking down. "They shouldn't worry about sudden, catastrophic engine failure," he said. "That is a misplaced fear."

Why would Jiffy Lube stick to the 3,000-mile recommendation for so many years after it became obsolete? And why would they announce switching to a new, more accurate guideline but then fail to do so in practice?

"I can certainly understand how you'd be confused by that," said Linington when I told him about all the misinformation I received when calling the 77 Jiffy Lube shops. "We called several Jiffy Lube locations after your e-mail and didn't receive a different experience ourselves." So Jiffy Lube executives were getting misinformation from their own employees? "Yes. Customers don't typically call the stores," he explained. "This OCS [oil change schedule] experience almost entirely happens at the store." But, he added, "from my perspective, it's not acceptable to get a different answer over the telephone than in the store, so I'm quite glad you brought this to our attention."

Virginia Sanchez, a public-relations representative for Shell Oil who was also on the phone, chimed in: "We want to thank you for identifying that opportunity to improve our customer service."