Ernie Craige pointed to the carburetor and asked, "Does anyone know what this does?"

The six students gathered around him and his 1962 Valiant in a parking lot at Sidwell Friends School squirmed uncomfortably. Not only did we not know what it did, we didn't even know what it was.

Craige, a soft-spoken and ever-patient Southerner, led our class of mechanical half-wits through five Saturday-morning sessions in Basic Auto Maintenance. He unraveled the mysteries of valves and pistons for a group that had never even changed a tire, much less looked into an engine.

A price run-down shows the advantage of learning at least simple maintenance tasks. An oil change at a garage generally costs $12.50 for labor alone; $55 is standard for a tuneup; $5 to replace a fan belt.

I'm not ready to try a valve job, but by the end of the course I was able to change the oil in my car, check its fluid levels and give it a simple tuneup. When I do take my car to a garage, mechancis no longer sound like they're speaking to me in a language in which the only words I recognize are the ones that say how much I'm going to have to pay.

"I can't show people common sense," says Dick Lee, a mechanic who teaches for the Open University. "But I can try to make them understand how an engine works." During a typical session he devotes an hour to discussion in the classroom and the rest of the time to tinkering on students' cars. "It's back and forth, back and forth between the abstract and the concrete."

Lee anthropomorphizes the car's parts, drawing parallels between human and automotive functions. "That's what worked for me," said Sally Popper, who took Lee's course with her husband, Lewis. "I could understand what I should do for my car when it gets wet by thinking of what I need when I get wet and cold."

According to Lee, three types of people take his auto-maintenance courses.

"The first don't plan to get grease under their fingernails at any cost. They just want peace of mind that they know what's going on with their machine.

"The second would like to work on their own cars, but have never held a tool. I can show these people how to do basic jobs and suggest that they follow up my course with a lot of puttering around.

"The third group can already use tools but lacks any theoretical framework. As a teacher, I can probably help this group the most."

Auto-maintenance students tend to look upon their teachers as technological miracle-workers, illuminating a world that had been vaguely sensed but never understood. Lee's students, no matter which category they fall into, are no exception.

"God didn't make cars when he made man," laughs Lewis Popper, a lawyer with a professed "non-technical" bent. "One of the most exciting moments of the course was when Dick showed us where the gas actually went in an engine. It all came together. This thing is what pushes everyone around!"

Neither of the Poppers has joined the ranks of do-it-yourselfers, but Sally plans to change the oil in the family car and Lewis "acts friendlier" toward it. In addition, he feels more prepared now to tackle a legal case he has pending that involves an automobile company.

Classmate Melinda Harris, on the other hand, decided, "If some of the mechanics I've met can work on cars, then I can, too." She works on her car or a friend's every Saturday, frequently returning to Lee for assistance.

"Sure, I feel proud when I've done something new," she said. "But the real reason is financial. I have better things to do with my money."

Lee himself had what he terms "undirected mechanical aptitude" until he realized that the job prospects for philosophers, which he studied to be at University of Maryland, were dismal. "I read books, I worked on people's cars. I made a lot of mistakes I cussed a lot and I still do."

Many area colleges and communities offer courses aimed at the consumer who doesn't know a distributor from a gas-tank cap. There are also specialized courses, of course, for those who already have the basic mechanical know-how.

Even knowledgeable driveway mechanics find automative independence out of reach without a prohibitive investment in tools and work space. Nowadays, however, rental facilities are springing up to make do-it-yourself a reality.

At Auto-U-Fix-It, hidden among the car dealerships and gas stations that line Bladensburg Road NE, George Lucey, the "president, treasurer, bookkeeper and anything else you want to call me" of the business, rents out 17 bays at a moderate price and supplies his customers with tools "as long as they keep them clean." And, when asked, he's available with tidbits of advice, but from tuneups to transmission jobs, it's the customer who wields the ratchet wrench.

Patience is the quality most frequently cited by mechanics as an aid to tackling projects major and minor.

"If your car doesn't work," says Lee, "you try the most logical thing that can be wrong. If that's not it, you try the next most logical. If that's not it, you have a cup of coffee and go back and try the third most logical.You can't get mad at a car."