how long does gasoline last in a car

[DelMarcus]

Gasoline typically lasts for about 3 to 6 months in a car's fuel tank under normal conditions. However, this timeframe isn't absolute and can be significantly shorter due to factors like the fuel's ethanol content, climate, and the age of the vehicle. The primary reason for this degradation is a process called oxidation, where fuel components react with oxygen, leading to the formation of varnish and gum that can clog fuel injectors and filters. Using a fuel stabilizer can extend this lifespan to up to 1-2 years for stored vehicles.

The biggest factor affecting fuel life is the ethanol blend. Most gasoline in the U.S. is E10 (10% ethanol). Ethanol is hygroscopic, meaning it absorbs moisture from the air. This water can separate from the gasoline in a process called phase separation, especially in humid environments or with temperature fluctuations. This contaminated fuel can cause corrosion and engine starting issues.

For long-term storage, such as for a classic car or seasonal vehicle, proper preparation is key. Here’s a quick guide based on storage duration:

Storage Duration	Recommended Action	Key Consideration
Less than 3 months	Fill the tank with fresh fuel to minimize air space and condensation.	Use a fuel stabilizer for added protection, especially with ethanol blends.
3 to 12 months	Fill the tank nearly full and add a high-quality fuel stabilizer.	Run the engine for 5-10 minutes to circulate the treated fuel through the entire system.
Over 12 months	Consider draining the fuel tank and fuel lines entirely.	For professional or collector vehicles; this prevents any potential for gumming.

If you suspect your gas is old, signs of trouble include difficulty starting the engine, rough idling, stuttering under acceleration, and a noticeable drop in fuel economy. For a car that's been sitting for over six months, it's often safest to have a mechanic drain the old fuel before attempting to start it to avoid costly damage to the fuel system.

[SanSteven]

From my experience, you can count on gas being good for about three months, maybe four if you're lucky. After that, it's a gamble. I learned this the hard way when I left my truck sitting all winter. Come spring, it wouldn't start. The mechanic said the gas had gone bad and gunked up the fuel line. It was an expensive lesson. Now, if I know I won't be driving for a while, I always add a bottle of fuel stabilizer. It's cheap insurance.

[Evelyn]

Think of gasoline as a perishable item. Its useful life is highly dependent on the environment. In a hot climate, the lighter components evaporate more quickly, degrading the fuel faster. In a humid climate, the ethanol in the gas absorbs water, which can sink to the bottom of your tank and cause rust and corrosion. A full tank leaves less room for air and moisture to accumulate, which helps it last longer than a near-empty tank. For most daily drivers, it's not a concern, but for seasonal vehicles, it's critical.