Debunking the "gas cap" urban legend (archive)

Folks have been nonchallantly saying "Check your gas cap" for months. ALmost everytime, the response comes back "I checked it...there was no problem."

So where did this gas cap theory come from. I've read no anecdotal evidence to suggest that the gas cap has been EVER proven responsible. Furthermore, my limited knowledge of the Service Light Soon light seems inconsistent with a gas cap being loose. What I mean is that there is no sensor that would be sensitive to gas tank pressure, to my knowledge. And finally, the gas cap theory really makes no sense. Surely, the gas tank pulls a slight vacuum as it is drawn down, but there is no such vacuum right after filling, so why would a car care exactly what pressure level was present in the gas tank.

My final coup d' grace argument to defeat the "gas cap" myth: The dealers themselves have told car owners that they need to tighten their gas caps to solve the erratic Service Engine Soon light. Dealers are particularly fond of these kind of unprovable, irrational, black magic explanations because it shifts the blame from the car to the the owner or to an Act of God.

David

Follow Ups:

Here's an idea...(m) George Wallerich 330Ci 03:51 5/07/2001 (3)
- Oh come on now. Do you try everything you read? dl 07:14 5/07/2001 (2)
  - Ooohhh. 3 Miles...(m) Cush325Ci 07:45 5/07/2001 (1)
    - Heh, I know...the post was a bit tongue incheek dl 11:06 5/07/2001 (0)

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