Quick answer: Sugar in a gas tank usually does not dissolve in gasoline , so it tends to settle out instead of “turning into sludge” in the engine. If enough of it gets picked up, it can clog the fuel filter or fuel injectors , causing stalling, poor acceleration, or a no-start condition.

What actually happens

  • Sugar does not mix well with gasoline. It generally sinks to the bottom of the tank rather than dissolving.
  • The main risk is blockage, not chemical destruction. If sugar is drawn into the fuel system, it may clog the fuel filter or injectors.
  • The engine usually is not “ruined instantly.” The old story that sugar melts into caramel and destroys the engine is mostly a myth.

Likely symptoms

You might see:

  • Rough running.
  • Loss of power.
  • Stalling.
  • Difficulty starting.
  • A no-start condition.

What to do

If this actually happened to a car, the safe move is to stop trying to start it and have the tank and fuel system inspected and cleaned by a mechanic.

Bottom line

Sugar in a gas tank is bad news , but not for the reason people usually think: it is more likely to clog the fuel system than to chemically “destroy” the engine.

TL;DR: Sugar usually sits in the tank, and if it gets into the fuel system it can clog filters or injectors.