The question of whether sugar dissolves in gasoline is often fueled by urban legends suggesting it can instantly destroy a car’s engine. While the idea of a sugary mess seizing an engine sounds dramatic, the true chemical and physical interactions between sugar and fuel are subtle. Understanding the core principles of chemistry provides the direct answer and explains the actual consequences of introducing sugar to a vehicle’s fuel tank.
Solubility and the Physical Result
The definitive answer is that sugar (sucrose) does not dissolve in gasoline, or it does so only in trace, negligible amounts. A 1994 experiment found that less than a teaspoon of sugar could dissolve in a full 15-gallon tank of gasoline. This small amount is chemically insignificant and will not form a sticky, dissolved syrup as the myth suggests.
Since sugar is insoluble, it remains in its original granular state. Sugar is also significantly denser than gasoline, causing it to quickly sink to the bottom of the fuel tank through sedimentation. This forms a layer of solid sediment on the tank floor, accumulating where the fuel pickup tube is located.
Understanding Polar and Nonpolar Chemistry
The reason sugar and gasoline do not mix lies in the fundamental principle of chemistry: “like dissolves like.” Molecules are classified as either polar or nonpolar, and a solvent can only effectively dissolve a solute if they share the same polarity. Gasoline is a complex mixture of hydrocarbon molecules, such as octane, which are inherently nonpolar.
Sugar (sucrose) is a highly polar molecule due to the presence of multiple hydroxyl (OH) groups. These groups allow sugar to form strong attractions, or hydrogen bonds, with other polar solvents like water. Because nonpolar gasoline molecules cannot form strong attractions with the highly polar sugar molecules, the sugar remains solid and will not enter into a solution.
Clogging and Fuel System Damage
While sugar does not dissolve, its presence as solid sediment creates a significant mechanical problem for the fuel system. The fuel pump draws fuel from the tank floor, and as it does so, it inevitably pulls the granular sugar particles into the fuel line. The first point of failure is typically the fuel filter, which is designed to trap debris and impurities before they reach the engine.
The fine mesh of the fuel filter quickly becomes clogged with sugar granules, restricting fuel flow to the engine. A blocked filter can lead to engine performance issues such as:
- Stalling
- Surging
- Rough idling
- Complete failure to start
If an excessive amount of sugar is added, or if the initial filter is bypassed, the fine particles can travel further down the line. They may obstruct the delicate nozzles of the fuel injectors or the jets in a carburetor. This obstruction prevents the proper atomization of fuel, ultimately requiring an expensive cleaning or replacement of the affected components.