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Gasoline

4 min read

Parent
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Fuel Types & Properties
What burns in what, and shelf life realities
Current
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Gasoline
Volatile, 3-6 month shelf life, stabilizer options

Gasoline loses its volatile fractions, gums up as it oxidises and, in ethanol blends, can separate into a water-alcohol layer, so it spoils over months rather than years, faster in warm or open storage and slower in sealed, full, stabilised containers. Judge it in a clear jar: dark colour, a sour varnish smell, sediment or visible layers mean it is degraded, and it should be filtered and diluted with fresh fuel or used in a tolerant engine, never tested by lighting a sample.

Part of Fuel Siphoning & Storage

Gasoline is the fuel in most abandoned tanks and the one that spoils fastest, through evaporation, gum formation and, in ethanol blends, water uptake.

Gasoline Spoils In Three Distinct Ways

Evaporation of the light fractions. The parts of gasoline that vaporise easily are the parts that let an engine start. From a loosely closed container they escape first, leaving a heavier liquid that starts hard. This is the same property that makes gasoline vapour dangerous, so a container that vents also releases flammable vapour.

Oxidation and gum. Over time the molecules react with air and form gums and varnish. These show as a darker colour and a sour, varnish-like smell instead of the sharp hydrocarbon smell of fresh fuel, and as sticky residue on container walls. Gum clogs carburettor jets and injectors.

Water uptake in ethanol blends. The parent article describes gasoline with 10% ethanol absorbing atmospheric water and separating, a process called phase separation. A water-alcohol layer settles at the bottom of the container. That layer does not burn properly and corrodes fuel systems.

How long. The parent article gives 6-12 months in a sealed container at moderate temperature for pure gasoline, 3-6 months for E10, and with stabiliser 12-24 months for E10 and up to 36 months for pure gasoline. Treat these as indicative only: temperature, headspace and container seal dominate, and no figure replaces looking at the fuel.

What You Need

  • A clear glass jar with a lid, clean and dry.
  • A funnel and a filter of fine cloth or paper.
  • Fresh gasoline if you have any, to dilute with.
  • Fuel-rated containers for the filtered result.

Method: Inspect The Fuel In A Jar, Then Decide

Step 1: Take a sample outdoors, from just above the bottom of the container, into the clear jar. Close the lid.

Step 2: Look. Fresh gasoline is clear to light amber. A dark amber or brown colour, cloudiness, floating particles, or two visible layers is degradation. A water-alcohol layer sits at the bottom and has a different look from the fuel above it.

Step 3: Smell, briefly. Waft the vapour toward you; do not inhale deeply. A sour or varnish note means oxidation.

Step 4: Decide.

  • Clear, correct smell: usable.
  • Dark or sour, no layers: filter it and dilute it. The parent article suggests mixing with fresh gasoline 50/50; expect reduced power and a risk of fouled jets or injectors.
  • Visible layer at the bottom: draw the top layer off carefully with a pump and leave the bottom layer behind. Never pour the bottom layer into an engine.
  • Thick, gummy or opaque: not fit for an engine. Seal it in a labelled container as waste, away from ignition sources and living space.

Common Mistakes

  • Testing by lighting a sample. You learn very little and risk burns. The jar and nose are enough.
  • Using the last portion of a container. Water and gum collect there.
  • Adding stabiliser to fuel that has already spoiled. Stabiliser slows degradation; it does not reverse it (see Fuel Stabilization & Treatment).
  • Mixing old and new fuel to hide the problem in a stored container. Dilute only to use it immediately.

Safety

Vapour, not liquid, is what explodes

Gasoline gives off vapour that is heavier than air, pools in low places and ignites from a spark, a hot surface or static across a wide range of concentrations. Open and inspect samples outdoors with no flame nearby. Never use a flame to test fuel or to check for vapour. Keep gasoline off skin, because it degreases it and is absorbed; wash with soap and water. If any is swallowed, do not induce vomiting, because aspiration into the lungs is worse than stomach exposure; rinse the mouth and get medical help if any is available.

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