Dear Tom and Ray:

I am looking to you to validate or refute a family myth. My father-in-law and mother-in-law believe in the phenomenon of sludge at the bottom of the gas tank. The family myth goes that you should never allow your tank to go below one-quarter full or all the sludge will get sucked up into the engine and destroy it. I always thought this was a myth designed by parents who didn't want their kids to run out of gas, and I dismissed it completely. But recently, my older sister revealed that our dad had told her the same thing! Is it true, or did two sets of parents on opposite coasts come up with the same urban myth? -- Sharon

Ray: I guess this myth has gone bicoastal, Sharon. While there usually is some condensed water at the bottom of the tank, that small amount of water doesn't do any harm in the engine. And while there are often flakes of rust because of that water, there's a filter that prevents them from getting sucked into the engine and ruining it. So it is a myth.

Tom: Plus, the thing that most people don't realize is that you're ALWAYS sucking gas from near the bottom of the tank. Why? Because that's where the pickup sits.

Ray: It has to sit there. If the gasoline pickup (the tube that sucks the gasoline out of the tank) was at the top of the tank, it would only work when the tank was completely full, right? Think about it.

Tom: And I think you're right that this "never let it go below a quarter tank" myth served the interests of parents, who a) didn't want to have to pick up the kid when he ran out of gas in East Armpit at midnight, and b) didn't want to get in the car the morning after junior borrowed it and find no gas in it (a teen-age tradition celebrating its 100th anniversary this year along with the automobile).

Ray: Now, having said all that, we should add that while running down below a quarter tank doesn't do any harm, running completely OUT of gas can do some damage (and we're not just throwing this in for the sake of all the parents of teen-agers who got mad at us in the last paragraph). We've seen a number of cases in which the electric fuel pump has been ruined by having been run on empty. Why? Probably because the pump uses the fuel as both a lubricant and a coolant.

Tom: So here's the story in a nutshell, Sharon. You have our permission to run your car down below a quarter tank as often as you want to. Just don't expect either set of parents to be real sympathetic when you call them for a ride -- or a new fuel pump -- when you DO space out and run out of gas, OK?

* * *

Tom: Well, you asked for it, and here it is. My brother and I sat down and wrote down everything we know about how to make your car last forever.

Ray: And it only came out to eight lousy pages!

Tom: But now this gold mine of information can be yours....

Ray: Get your copy of "Ten Ways You May Be Ruining Your Car Without Even Knowing It!" by sending $3 and a stamped (55 cents), self-addressed, No.10 envelope to Ruin No.1, PO Box 6420, Riverton, NJ 08077-6420.

Everybody wants a new car. But from a purely financial point of view, there is no question that buying a used car is always cheaper, even in the long run. To learn more, order Tom and Ray's pamphlet How to Buy a Used Car: Things That Detroit and Tokyo Don't Want You to Know. To order, send (check or money order) to Ruin, P.O. Box 536475, Orlando, FL 32853-6475. You can also order online.

© 1997 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

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