710 cap

A blonde walks into an auto parts store and says to the dealer "I need a "710" cap."

"What?" the dealer is confused. And she says again "I need a "710" cap."

The dealer tells her to let him go get his manager.

So he comes back wit his dealer and he asks what's the problem. She tells him that she needs a "710" cap.

He's also confused. So he asks to look at her car.

So they go outside and she says "here's the "710" cap that goes there."

(Look at "710" upside down) and sure enough it says "OIL"