Should I turn off the AC before turning off the engine?

Dear Car Talk

Dear Car Talk | Aug 01, 1996

Dear Tom and Ray:

We've just purchased a new Ford Ranger pickup. The salesman told us the air
conditioner should be turned off before turning off the ignition when we
park the pickup. He said something about it making the O-rings last longer.
We could find nothing in the owner's manual about this. What do you think?
-- Joyce

RAY: Well, this salesman is obviously a rocket scientist. He must have
worked on NASA's space shuttle program since he's so intimately familiar
with O-ring technology.

TOM: Actually, he's nuts, Joyce. I think he's suffering from PMS: Post
Manipulation Syndrome. He knows he's just done a song and dance and talked
you into buying all kinds of stuff you don't need: the power moonroof, the
pin-striping, the crushed Corinthian interior. And now that he's actually
talked you out of your money, he's feeling a little bit remorseful.

RAY: Not remorseful enough to give you any of it back. But he does want to
ease his conscience by giving you something. So what does he give you?

TOM: Lame advice, as it turns out, but advice nonetheless. Turning off the
air conditioner before you turn off the engine makes no difference to the
air conditioner or the engine.

RAY: He probably doesn't even know his advice is useless. He's in a
remorseful, cathartic trance after the sale, so he really can't be held
responsible for his actions. Just pat him on the shoulder and tell him to
give 100 bucks to charity when he comes to.

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