A Staff Report from the Straight Dope Science Advisory Board

Followup: are you sure sugar in the gas tank will wreck a car engine?

Dear Straight Dope:

Read your answer to question about wrecking car engines via sugar in the gas tank. Hate to question the mighty brain but am wondering about your sources because I read an article in Motor Service magazine (automotive trade publication) about a year ago concerning this same question. They ran some actual tests on an engine and the result was NOTHING. The first part of your own answer holds the clue - the sugar does not dissolve in the gas. It simply falls to the bottom of the tank and stays there, never getting to or through the filter to the pump or anywhere else. Your comment about sand into the oil filler was right on and in fact sugar in the same location would also be effective as it is hard enough to abrade the parts initially and then as it breaks down and becomes heated by the engine it will begin to carmelize leading to the sticky mess you described. I'm quoting this from memory but I remember it pretty well as the first definitive answer I'd ever heard on the common myth. If you have definite conflicting sources I'd be interested in learning more and how they obtained there data. My interest certainly is academic but I remain curious.

Chuck, an inquisitive mind is a good thing. Makes the world go around and keeps Unca Cecil in the paydirt. I have EXTREME conflicting sources with Motor Service (circulation, please?). My original sources were actual mechanics and auto salvage yard operators. The five I spoke with had a total of over 150 years of automotive experience. Two admitted that they had, in the past, actually perpetrated the sugar trick and seen the successful results - one cackled gleefully at the memory. That was enough for me ... but since you asked, I did a little SDSAB experiment of my own.

The vehicle utilized was a 1983 Cutlass Ciera with 94,000 on the clock and a mortal lifter knock. Along with my assistants, we lowered the gas tank and pulled the fuel pump (the pump is mounted on the tank these days). Hmmm, about 1/4 full. Excellent. In went a healthy amount of Domino's Refined Sugar ... not enough to touch the fuel pump sock. Back went the the pump. Gentlemen, start your engine. After 10 minutes, I began to get nervous. But at the 16 minute mark, the motor made the first of what would prove to be a series of hiccups. Twice it stalled and had to be restarted. At 31 minutes the engine quit and would not restart until we fired it up and kept it running by squirting a steady stream of starting fluid directly into the carburetor. Clearly, fuel was no longer coming from the fuel tank. When the pump unit was removed for re-examination, the sock was caked with sugar and the pump sounded a tad ill when juice was applied. It would be interesting to learn the conditions under which Motor Service magazine failed to achieve this result. Those who had supplied me with the earlier information merely shrugged and said, "I told you so." They also waxed nostalgic on the old golf ball trick. While I go get the Go-Jo to get the gas smell off my hands, let's all pause a moment and sigh happily that at least one urban myth is not a myth at all.

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