I a moving into a new car this week.

I have poured the last can of oil into the insatiable beast and taken the last nostalgic trip through the neighborhood. As soon as I finish packing the last box, I shall be ready for moving day.

But why, you ask, would a person need packing boxes to move out of a car? A car after all is not a house, despite the fact that it costsd as much as a decent down payment.

The truth of the matter is that I, an otherwise neat person who keeps her clothes and her copy clean, have a secret mobile life.

I am the shopping-bag lady of the auto world. I belong to a subcategory of Americans who are not closet slobs, but rather car slobs.

We are sort of people you don't want to have move into the parking space next to you. Believe me. Sooner or later, we turn every car into a slum.

I am not alone in this. Although there is no particular support group for my felow slum drivers in this car-obsessed world, I can spot the others at any red light or parking garage.

There are the telltale gypsy moth droppings on the roof, the venerable ice cream cones next to the babe seat, the tattered bumper sticker of days gone by: "Don't Blame Me, I'm From Massachusetts." That sort of thing.

Slum drivers are people who know not the wonders of hot wax, who have their car washed only when the seventh grade is fund-raising. If confronted, some of us deny it. One insists that she is merely saving dust samples for her geology class. Another swears that he is growing cultures out of his son's cookie crumbs.

But, like other sinners, we recognize each other for the terrible things we do in our cars. I'm not talking about sex in the back seat. I'm talking coffee all over the front seat.

On moving day I will excavate the items currently living in my motor vehicle. This task requires a certain archaeological skill.

To begin with, there is the hatchback of many wonders. If you dig through the goodies destined to these many months for the Salvation Army, you come across a snow-scraper. This is a particularly handy item in July.

To the left of it is the ubiquitous umbrella. This is the only umbrella I have never lost, since in four years it has never left its cozy spot over the spare tire.

Below these two items, on the floor of the hatchback, are assorted newspapers. These are part of an experiment I am conducting to determine how quickly a newspaper yellows. For your edification, the one dated Oct. 18, 1977, has a fine brittle quality to it that is rarely reproduced outside of Egyptian museums.

Moving forward, into the back seat, I also find the sneakers that I bought for jogging in 1978. These have logged some 30,000 miles . . . in the car. Add to these intriguing artifacts two barrettes, one earring. a sweater I took off in November 1980 and a squash ball, and you have your everyday items for shopping -bag car ladies.

Now on to the front seat. Aside from two-dozen normal magazines being transported between home and office, we find here two vintage $15 parking violation notices awaiting summons, and a raft that sprang a leak in the summers of '79.

Suffered between the clutch and the passenger seat we see a dozen ordinary credit-card receipts and parking stubs and a ball point pen that leaks ink. This is so I will be ready if I am audited while driving past the Internal Revenue Service. There are also several candy wrappers, But I have no idea where they came from. I suspect some pervert left them there to cast aspersions on my willpower.

Once I pack all these scraps of my past, the best thing to do would be to throw them out. I could have a clean slate, new resolve. But it occurs to me that I shall have to start all over again, creating that unique sense of history, of warmth, of the messiness that is me-ness.

Perpaps I will simply move them with me. I think that the peach pit on the dash could lend a real homey touch.