The average cost of a 1978 car is a whopping $5,780, according to the National Automobile Dealers Association.

On the surface, it would appear that many prospective buyers couldn't afford a new car this year. In the fall of 1970, the average new car only cost $3,430.

But this big price jump is deceptive. While car costs have spiraled, so have average wages. The Bureau of Labor Statistics says the average hourly wage is now $5.25. In the fall of 1970, the average wage was $3.22 an hour.

When you work it out, the average worker must be toil for 635 hours during the year to be able to own and operate a new car. But when you compare this with the 610 hours it took to own and operate a new car back in 1970, it's not much of a difference.

Still, it's somewhat shocking when you realize the average worker in this country has to labor nearly 16 weeks out of the year just be able to support a car.

Here's how it breaks down:

With an average price of $5,780 for the 1978 cars, the average monthly payment comes to around $170 or $2,040 a year.

When you add $375 for gasoline (at 10,000 miles per year), $400 annual repair and maintenance costs and the average $520 insurance tab for urban driving, you get a $1,295 annual operating costs. Combining this with annual loan payments, you get a total cost of $3,335 a year for the average worker to own and operate the average 1978 car.

Going back to 1970, it cost $110 a month for car payments, or $1,320 a year. Gasoline averaged $170, insurance $330 and repairs of $650. When you added this to the $1,320 annual loan payments, you got a total $1,970 to own and operate the average car in 1970.

But the average worker only got $322 an hour in 1970, required 610 hours of work to own and operate the average new car. So the amount of work it takes the average new car paid for and on the road has stayed pretty much the same over the years.

If you consider the fact that today's cars are higher quality products than their 1970 counterparts, it might take even less work to pay for the privilege of ownership.

The Bureau of Labor Statistics has worked up figures that show that the quality-weighed price for new cars has gone up less than actual striker price.

BLS contends that new car owners are getting less pollutants coming out the exhaust pipe, more safety features and using less gasoline. you're paying more, but you're getting more car.

Even though it's going to cost you $3,335 to own and operate the average new car, automobile manufacturers are counting on the fact that your increasing wages will cover the payments and maintenance bills.

And the manufacturers are hoping that the emphasis on fuel efficiency will tempt you into trading your old gas guzzler for a new car bigger. Now they charge you more for making a car smaller.

Q. What chemicals do I use to treat shredded paper so it can be used as a cheapo insulating material? I have mountains of old newspapers.

A. The chemicals used by companies to make commercial insulating masterial from shredded newspapers are patented and are a closely-guarded secret. It's a tricky business, according to the National Bureau of Standards, and is no place for the amateur.

Chemicals used to treat shredded paper for insulation must make the material fire-resistant and must not lose this quality through leaching caused by dampness. If flame-ratardant chemicals come in contact with water and an electrical charge, you could end up with a fire hazard.

When you use commerically processed cellulose (shredded paper) for insulation, be sure that it does not come in contact with electrical outlet boxes. There's usually a warning on the bag but not everybody pays attention to it.

Q. Our house has two complete living areas - one one on each floor. We won't be renting out the upstairs unit this fall and would like to know if there's any way of shutting off the hear upstairs and insulating the downstairs unit so we won't have such a big fuel.

A. You have to be especially careful with your upstairs plumbing. You don't want it to freeze. Have a plumber check to see if it can be shut off and to see if you can insulate pipes that may become exposed to the cold.

You can have a local insulation company come in and blow insulation between your downstairs ceiling and your upstairs flooring. While the contractor is at it, you might want insulation blown into your downstairs walls as well. This would give you a completely insulated downstairs unit.

You could put wall-to-wall carpeting upstairs, but it would only give you a fraction of the insulation you'd get from a proffessional insulation job. You could also put down a temporary layer of mineral wool insulation "blankets" upstairs but the whole thing would have to be removed when you decided to use the unit.