DEAR CARS: In the late 50’s and early 60’s, I think I remember seeing cars in Southern California with straps hanging underneath them touching the road.

Were these straps really necessary, and if so, what was their purpose? And what has changed, because you certainly don’t see them anymore. — gender

DEAR READER: Fads come and go, Paul. Now, instead of dangling ribbons, we have decals of a peeing kid. The March of Progress, right?

The answer is that they were not really used for passenger cars. They were decorative. Their supposed purpose in the 1950s and 1960s was to discharge static electricity built up in the car so that when you get out and touch a metal door handle or frame, you don’t set off a 2-inch spark and straighten your new curl.

But they did nothing. Some people just thought they looked cool and maybe believed the advertising copy on the packaging.

Static electricity builds up in the car – especially when you drag your polyester pants across the seat to get out. But you already have equipment designed to conduct static electricity to the ground: your tires.

There was a period, about 20 years ago, when manufacturers replaced carbon black, a highly conductive material used to harden rubber tires, with a different booster called silica.

They switched to silica because it created less rolling resistance with the road. If you can make a tire that holds the road well when cornering and braking, but generates less friction when it’s just rolling, you increase gas mileage.

But silica did a worse job of discharging electricity, and some customers complained of static shocks. So manufacturers adjusted their formulas and now use enough carbon black to allow for good static discharge.

But, believe it or not, these straps are still being sold. And somewhere, the great-grandsons of the armor-strap king are sipping margaritas by a pool, reveling in their generational wealth. Along with their neighbor, the inventor of the mood ring.

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DEAR CARS: I own a 2012 Chevy Equinox with a four cylinder engine. These cars are notorious for using oil.

My car burns oil but apparently does not meet the Chevy oil requirement to replace the defective rings under warranty. Now, with 115,000 miles on the odometer, I use a quart of oil every 1,000 miles.

Here’s what I think: A car’s oil life monitor usually calls for an oil change every 8,000 miles. The car has 6 liters of oil. I add 8 liters of oil between shifts. So why should I change the oil at all?

Since the car burns old oil and gets a steady supply of fresh oil, I never have to change the oil again, right? I exceed the manufacturer’s requirements! Am I correct in my thinking or am I missing the obvious? — Steve

DEAR READER: It’s a good theory—but like many theories that sound good to their creators, this one doesn’t stand up to scrutiny.

Here’s the part you’re missing: As you burn oil, what you leave behind is the dirt, sediment, carbon, and metal fragments that have been held in suspension by that oil.

Imagine chopping some garlic and putting it in a pan with some olive oil. When the oil runs out and you feel burnt, pour a little more olive oil into the pan.

Now, if you continue to do this for, say, 15 days, will the pan be clean? No. This garlic will be “one” with the bottom of the pan even though you keep adding fresh oil.

The same thing happens in your engine. You add fresh oil, but the oil that is there becomes more and more concentrated with contaminants.

How to get rid of it? You change the oil. Drain it, dirt and all, and replace it with clean oil.

In fact, when you’re burning oil, it’s even more important to change your oil regularly for this very reason – so you don’t build up excessive dirt and sludge.

You may even find you burn less oil after an oil change, Steve, since clean oil doesn’t burn as easily. Try it. And write again if you have more cooking questions. I’ll be here.

Ray Magliozzi hands out car tips on Car Talk every Saturday. Email him by visiting