What Happens if I Put Sugar in Someone's Gas Tank?

By: Kristen Hall-Geisler  | 
sugar in gas tank illustration
Will sugar turn into cement in your gas tank? HowStuffWorks

For some reason, there's a common rumor about sugar and gas that's been around for decades. Supposedly, if you pour sugar into someone's gas tank, you will disable the car. The sugar is supposed to react with the gasoline and turn into a semisolid, gooey substance that totally clogs up the gas tank, the fuel lines and so on.

It may sound great, especially if you have a grudge against someone. The problem with this rumor is that it simply isn't true.


How Fuel Filters Help

For starters, you have a fuel filter. This does exactly what it says: filters out any debris or impurities that might have gotten into your gas tank somehow. So if there were little sugar crystals in your gasoline, the fuel filter would stop them before they could damage the engine.

Then there's the fact that plain old sugar does not dissolve in gasoline; it just sinks to the bottom of the gas tank.


A University of California, Berkeley researcher tested this myth experimentally way back in 1994 by putting sugar into gasoline and then spinning it in a centrifuge. He measured how much undissolved sugar spun out of the fluid and then calculated how much sugar remained dissolved in the gasoline. It was less than a teaspoon for 15 gallons of gas – more than a full tank in many cars.

Even if you have less than a full tank and someone dumps sugar in there, the fluid can only incorporate so much sugar. You'll just have more undissolved sugar sludge at the bottom of the tank. Annoying for sure, but not damaging the engine.


How Fuel Pumps Help

Back when the myth started in the 1950s, fuel pumps were mechanical and located at the bottom of the fuel tank, so if there was a big glob of sugar there, it would stop up the flow of the fuel. The sugar wasn't getting into the engine, but neither was the gasoline the engine needed to run.

Modern fuel pumps are electronic, but it's possible they could be foiled by a glob of sugar. Again, it merely requires cleaning out the tank in either case.


More Dangerous Than Sugar

So, what will mess up an engine if it's added to the fuel? Water. But it would have to be a lot of it.

Remember that engines use combustion to make the wheels move, which means thousands of little explosions in the cylinders. If you pour a lot of water into a fuel tank, it sinks to the bottom of the tank. The water gets into the engine and, if there's enough water in the cylinders, the fuel does not combust. The engine is dead in the water, you might say.


But even this isn't the end of the road for your engine. Using a fuel treatment can chemically clear out the water and revive the engine.