How Long Does Fuel Last in the Gas Tank?
2 Answers
Fuel in the gas tank will deteriorate if left unused for more than six months. It is recommended to drain the gasoline from the tank, clean the tank, and then restart the vehicle. Introduction to Fuel Shelf Life: The usable duration of fuel in the tank depends on the fuel type. Regular gasoline has a shelf life of 3 to 6 months, while diesel can last up to a year before beginning to degrade. On the other hand, ethanol-based organic fuels, such as E10 gasoline with 10% ethanol content, lose combustibility within just one to three months due to oxidation and evaporation, making them the shortest-lived. Identifying Deteriorated Gasoline: When gasoline ages, its chemical properties change. The engine ECU cannot process the fuel correctly. If the gasoline has deteriorated, the engine warning light may illuminate in some vehicles due to abnormal combustion. Beyond the vehicle's computer diagnostics, deteriorated fuel can cause noticeable issues, including failure to start, ignition problems, increased vibrations at idle, or loss of power while driving, especially during acceleration. The condition of gasoline can also be determined by its color and smell. Deteriorated fuel appears darker and more turbid, emitting a sour odor. In such cases, the tank should be completely emptied. Deteriorated gasoline can damage internal engine components and leave gummy residues that may clog fuel lines.
The fuel in the tank generally deteriorates within three months to half a year, depending on storage conditions, as I learned from a friend who runs an auto repair shop. For instance, gasoline oxidizes faster in high temperatures, especially under direct summer sunlight, which accelerates evaporation and moisture absorption, shortening its lifespan. Humid cities also speed up deterioration because water mixing into the fuel can cause engine issues like hard starts or smoking. I always remind my neighbors that if a car will be parked unused for a long time, it's best to fill the tank to minimize air exposure or add a fuel stabilizer to prevent oxidation. A telltale sign of spoiled fuel is a sour or unusual smell at the tank opening after long-term storage—prompt action is needed to avoid engine damage.
