A DIVISION OF LABOR occurred naturally and early on in my marriage. I would take care of the income taxes. My husband would take care of the cars. I take considerable pride in the fact that our returns have never been rejected and he takes considerable pride in the fact that neither of our aging cars has ever broken down. So I waited until the children were in bed the other night to break the news to him.

"I have something serious to discuss with you," said I.

"What?"

"It's about my car."

"What about it?"

I took a deep breath. "Well, the alternator belt is frayed, there's a hole in the heater inlet hose, the voltage required for the ignition is high -- which means that there's probably something wrong with either the spark plugs or the distributor rotor -- and it needs a fron-end alignment." I certainly had his attention by then.

"What," he said guardedly, "is going on?"

"But," I continued, " the car is running super-clean, the ignition reserve is okay, the timing is right on and the idle speed is very good. Basically," I concluded brightly, "you've been doing a fairly good job."

Now, my husband knows perfectly well that unlike Sir Francis Bacon I do not take all knowledge to be my province and one area I've happily left to others is cars. He also knows that I had a terrible time figuring out how to screw on the gas cap that the gasoline station attendant had left on the roof of the car recently. An explanation was in order.

Our car was running 60 or so that were diagnosed by the Champion spark plug machanics at a Department of Transportation energy conservation fair this week. The idea behind the fair is that there is a lot drivers can do now to conserve gasoline. They can buy smaller cars with fewer options and avoid short trips less than five miles, which is the driving that is the least fuel efficient. But they can also learn driving habits that are fuel efficient and begin paying more attention to the maintenance and tuning of their cars.

"There's a lot you can do," says Anne Morris, a behavorial scientist with DOT. "They're all little things but you can cut back significantly.Everybody's looking for the quick technological fix. It's not there."

What is here is the fuel efficiency driving system and the energy efficiency maintenance program that have been developed through research and tests by private industry and government. And a lot of it is simple common sense.

According to the exhibitors, who ranged from the Maryland State Police to Atlantic Richfield, the fuel efficient driving system is based on the simple premise that cars use the least amount of gasoline when they are driven with a warm engine, in a straight line, with as little weight and wind resistance as possible. Things to avoid are sudden stops, jackrabbit starts, going over 55 miles per hour, lane-hopping and other unnecessary wheel movements, tailgating and roof luggage carriers that break the flow of air over the car. Avoid carrying unnecessary weight, such as the bag of sand that's in the trunk in case of a snowstrom.

Don't start the car and let it run five or 10 minutes to "warm up." Most cars need to be going only 30 seconds to be warm enough to run. After that try to reach cruising speed as fast as possible since that is the point at which cars operate most efficiently. Accelerating slowly waste gas. If the car will be idling more than one minute, it is more efficient to turn it off.

Keep the lightest possible touch on the accerlerator while maintaining cruising speed. Anticipate red lights and traffic stops so you can coast into them. Anticipate hills, and press down on the accelerator enough before going up the hill to maintain momentum. Don't increase speed while going up a hill, because that wastes a lot of gasoline.

Keep tires inflated to the maximum pressure (it's on the sidewall of the tire) and check pressure once a week. Soft tires cause the engine to work harder, which means it is using more gasoline. radial tires increase gasoline mileage. Use a multigrade oil.

"There's a lot individuals can do to conserve fuel, but they don't realize it," says Morris, who is with the energy policy division of DOT. "It's a whole new idea. It really means making people aware of what they're doing when they're transporting themselves. It's very hard to make people stop and think about something that is just such a routine type of activity. We have to make people start thinking of how to change their behavior.

"Essentially we're talking about raising their consciousness about transportation and providing them with the information they need to make the necessary changes. And then, they can go back to treating transportation as a routine behavior."

Carl Rappaport, a transportation specialist in the energy policy division, says the average car uses about 800 gallons of gasoline a year. He says a driver can save up to 40 percent in gasoline consumption by doing four things: select a vehicle and options with efficienty in mind, maintain the vehicle properly, drive it efficiently and plan trips to maximize fuel efficiency. In a nation of 100 million cars, this could mean a saving of 32 billion gallons of gasoline a year. "If you're assuming gasoline costs $1.25 a gallon," he says, "you would save $40 billion a year for the nation as a whole."

Back in the days of plentiful gasoline, we could afford the luxury of driving the way we wanted to. Back then it was considered almost unfeminine for a woman to know anything more than how to start the windshiled wipers. If we were intimidated by math, we were petrified by cars.

"Realistically," says Anne Morris, "there's no reason why women shouldn't know about a piece of equipment like a car."

No, there isn't. Unfortunately, however, the fuel conservationists have yet to resolve -- at least to each other's satisfaction -- the Big Question of the summer, the one that provokes no end of arguments along the vacation highways in July and August. Is it more efficient to cruise to the beach with the windows open, which produces a drag on the car, or drive with the air conditioner on?

Rapaport says the two options are fairly close. But when the argument starts, you're on your own.