A 58,000 liter fuel truck delivers gasolinr to a service station Photo KDG

A 58,000 liter fuel truck delivers gasoline to a service station
Photo KDG

A source says this truck , in the 40 degree heat a 6000 liter delivery may have been 5500 liters.

The holding tanks in a service station are in the cool ground and we estimate that the gasoline would return to its volume density fairly quickly, however if you have the choice and you know of a delivery you may get better value sometime after a delivery on a hot 40 degree day. Perhaps gas up would be better in the early morning hours in the current conditions.

Quality gasoline should be stable almost indefinitely if stored properly. Such storage should be in an airtight container (to prevent oxidation or water vapors mixing), and which can withstand the vapor pressure of the gasoline without venting ( to prevent the loss of the more volatile fractions), and at a stable cool temperature (to reduce the excess pressure from liquid expansion, and to reduce the rate of any decomposition reactions). When gasoline is not stored correctly, gums and solids may be created, which can corrode system components and accumulate on wetted surfaces, resulting in a condition called “stale fuel”. Gasoline containing ethanol is especially subject to absorbing atmospheric moisture, then forming gums, solids, or two phases (a hydrocarbon phase floating on top of a water-alcohol phase).

The presence of these degradation products in fuel tank, lines, carburetor or fuel injection components makes it harder to start the engine, or causes reduced engine performance. On resumption of regular engine use, the buildup is often eventually cleaned out by the flow of fresh gasoline. The addition of a fuel stabilizer to gasoline can extend the life of fuel that is not or cannot be stored properly. Some typical fuel stabilizers are proprietary mixtures containing mineral spirits, isopropyl alcohol, 1,2,4-trimethylbenzene,or other additives. Fuel stabilizer is commonly used for small engines, such as lawnmower and tractor engines, especially when their use is seasonal (low to no use for one or more seasons of the year). Users have been advised to keep gasoline containers more than half full and properly capped to reduce air exposure, to avoid storage at high temperatures, to run an engine for ten minutes to circulate the stabilizer through all components prior to storage, and to run the engine at intervals to purge stale fuel from the carburetor Source Wikipedia

We think that if you fill your tank in the current temperatures that filling to the top may not be advisable. However expansion of the tank in your vehicle is also a consideration.

Apparent and absolute expansion

When measuring the expansion of a liquid, the measurement must account for the expansion of the container as well. For example, a flask, that has been constructed with a long narrow stem filled with enough liquid that the stem itself is partially filled, when placed in a heat bath will initially show the column of liquid in the stem to drop followed by the immediate increase of that column until the flask/liquid/heat bath system has thermalized. The initial observation of the column of liquid dropping is not due to an initial contraction of the liquid but rather the expansion of the flask as it contacts the heat bath first. Soon after, the liquid in the flask is heated by the flask itself and begins to expand. Since liquids typically have a greater expansion over solids the liquid in the flask eventually exceeds that of the flask causing the column of liquid in the flask to rise. A direct measurement of the height of the liquid column is a measurement of the Apparent Expansion of the liquid. The Absolute expansion of the liquid is the apparent expansion corrected for the expansion of the containing vessel

Our final word is be more careful  with gasoline and its vapour in the heat. KDG

update: A comment from facebook:

Rory wrote: “Good article Kev. When I was towing, we would get calls from either the police or fire to tow away parked vehicles that were leaking gasoline caused by full tanks and heat expansion.”

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