Supposedly this really happened:

The other day I was in the local auto part store. A lady comes in and asks for a seven ten cap. We all look at each other and ask, "What's a seven ten cap?"

She says, "You know, it's right on the engine. Mine got lost somehow and I need a new one."

"What kind of a car is it?" they ask. Now I'm thinking maybe an old Datsun Seven Ten, but no, she says that it's a Buick.

"Okay, Lady, how big is it?"

She makes a circle with her hands about 3 1/2 inches in diameter "What does it do?" we ask.

She says, "I don't know, but it's always been there." One of us gives her a note pad and asks her if she can draw a picture of it. So she makes a circle about 3 1/2 inches in diameter and the center it had 710.

One guy says, "I think you want an oil cap."

She says, "Seven Ten cap, oil cap, I don't care what you call it. I just need one, and I don't see what is so funny about it."

Yes, she was a blonde.

If you read "710" upside down, it spells OIL!