Jerry cans for gas storage. Left: real metal jerry Can. Right: "approved" jerry can made from HDPE plastic.
I live in an area were we have at least once a year a power outage and I have a
small generator to handle those outages.
Batteries and inverters connected to a car battery are OK for short outages but they are not an option for outages that last days.
I used to keep only a small 5L canister with gas (gasoline, petrol in the UK) for the generator. Those 5 liters are good for the first 8 hours and I thought that I would simply drive to the next working gas station if I needed more gas.
I realized after an outage that lasted a full day that "driving to the next working gas station" does not work when you actually need more gas. Longer outages are longer because there is a more serious problem and it does usually affect a much bigger area. Finding a working gas station requires therefore a much longer drive, and roads blocked by fallen trees or flooded roads can make driving impossible. It's essential to store enough fuel to run the generator for several days.
Gas stability
Gas (gasoline, petrol in the UK) is a mixture and it does not last forever. It's made from raw mineral oil that is
millions of years old and one would think that it could easily last a few decades
without degrading but that's not the case. Today raw mineral oil is not just distilled into gasoline. A catalytic chemical reaction in "cracking towers" is used to split heavy
mineral oil into different short chain molecules. Not all of the resulting short chain molecules are stable. They can react with each other and form again longer chains.
It is this reaction combined with oxidation and the evaporation of some molecules that causes gas to form thicker jelly like substances over time.
Gas stations offer different fuel grades categorized by octane numbers but this is not
the only variable:
Gas is seasonal: The gas sold during cold Canadian winters has a different composition than the gas sold during the summer. Winter gas evaporates more easily. The best time to buy gas for long term storage is August to October.
The more expensive high octane gas is more refined: the hydrocarbons are of more even chain length and they remain stable over longer periods of time.
High octane fuels contain higher concentrations of detergents and other additives that help reduce carbon deposits and keep engine components clean.
The more expensive gas used to be ethanol free: The highest grade fuel sold at gas stations used to be ethanol free. Ethanol attracts water during storage. A of 2022 all gas stations in Canada may add ethanol to any gas.
How to recognize bad gas
Fresh gas is clear or dyed. Before 2022 I used buy Shell V91 and that is a slightly yellow liquid when it's new. It becomes autumn leave brown when it goes bad. At this point it is
still a liquid and you can use this older yellow-brown gas in your car. Add up to 10L of old gas to a gas tank that contains otherwise fresh gas and it will not cause any problems. Alcohol free Shell V91 (bought in Canada before 2022) could be stored in air tight containers
for 3 years before it started to turn slightly brown.
Buy Shell V91 between August and October.
Use 20L Jerry Cans and fill them with only 18L of gas. The air space is needed to have an expansion buffer. Without the buffer you would need to vent the gas can periodically which causes loss of gas and accelerates the process of gas going bad.
Rotate the stored gas every 1-2 years and use the older gas for your car. Add up to 10L of old gas to a gas tank that is at least half full and contains mostly new gas.
STA-BIL Storage Fuel Stabilizer or B3C Ethanol Shield
The main component of "STA-BIL" is an emulsifier. It prevents gas that contains ethanol form
from separating (aka phase separation). Ethanol attracts water and fuel with added ethanol contains water. This
ethanol water mix can not only react with short chain molecules in the gas but it
can also separate. STA-BIL ensures that the gas remains a homogeneous mixture as it ages.
"B3C Ethanol Shield" is kind of a stronger version of "STA-BIL". It's more difficult to find
but it works better. If you use gas cans that seal properly then any of the two will work because we are talking only about very small amounts of water.
These stabilizers contain also other proprietary components that are supposed to be helpful.
How they work exactly and what they are is unknown.
It's probably a good idea to add STA-BIL Fuel Stabilizer or B3C Ethanol Shield to high grade gas bought
after 2022 as now all grades of gas sold in Canada at gas stations can contain ethanol.
I have been asking gas station owners about the ethanol content of their gas and they
don't know. All of them talk about the high grade gas as "the best gas" but they don't
know if and how much ethanol it contains.
Note however that high grade gas with ethanol is something new. It could be that the
additives added buy gas stations contain now already something equivalent to "B3C Ethanol Shield" and "STA-BIL". It will take a few more year until we have some practical experience
with regards to the long term stability of high grade gas with ethanol.
Containers for storing gas
In Canada only plastic cans are approved for the storage of gas. Approved means that
a bureaucrat has been paid to approve it. It does not mean that this kind of container is the best option
for long term gas storage. Approved gas cans are made of ABS or HDPE plastic. Older Canadian plastic gas cans were often made by Wedco and the more recent ones are made by Scepter.
The advantage of plastic cans is that they are mechanically quite stable. However there isn't any
plastic material that is gas tight. Small hydrocarbon molecules can
penetrate truth the walls of those gas cans. These small molecules fit in-between the larger plastic molecules and this way they do slowly evaporate out of the can. This is the reason why plastic
gas cans smell. Over time you loose some gasoline volume when you store it in a fully closed plastic gas can.
The only two materials that are really gas tight are glass and metal. Glass containers
are a potential hazard because they break when you drop them but otherwise they would be a good option. Note that those glass bottles would have to have metal lids with seals that are not dissolving or expanding in the presence of gas fumes. It's not possible to buy shatter resistant rubber coated glass bottles with the right caps and seals but I have built myself such bottles out of clear 1L glass bottles. I consider them a safe option and those bottles allow me to see the color of the gas as it ages. This is how I found out that winter gas ages much faster than gas bought between August and October.
The US army uses metal jerry cans with 3 handles and a special locking system. They were invented by Germany and the US army adopted them. You can stack them and you can choose
how to carry them. The 3 handles allow you to: A) carry a single can with one hand by using the middle bar. B) carry two cans in one hand by putting the two cans next to each other and them grabbing them with one hand by the respective outer handlebar. C) carry one heavy can with two people by using the other handlebars (jerry cans filled with diesel fuel are quite heavy). These metal jerry cans do not gas off or leak. This is in my opinion the best option. Make sure you buy real jerry cans and not some low quality imitation. The metal has to be strong enough to prevent the can from bulging under pressure and the cans have to be painted on the inside to prevent them from rusting.
AVGAS is very stable and ethanol free
We can no longer buy real gas at gas stations for cars. All grades of gas contain now
ethanol. Aviation gas for small airplanes remains however ethanol free. It's called 100LL gas and it is available at small airports. The problem is that
this gas contains lead. Leaded gas is a bad idea but it would work for your generator or antique car. However you can't rotate Avgas 100LL it into a modern car with a catalytic converter. The leaded airplane gas would ruin sensors and catalytic converter.
Trufuel
You can however buy a gas known as Trufuel in small cans at hardware stores. This is real
gas without ethanol and it has a suggested shelf life of 5 years (it's probably good for longer). Trufuel costs about seven times as much as gas at the gas station but it's an option
if you want have a small amount of gas on the shelf for running your generator. Trufuel is an ethanol free gas with 92 octane.
One quart of Trufuel costs about 10$ but you can keep it on the shelf for 5 years (probably longer)
Filling your gas can at the pump
Most gas stations have pumps that allow you to select different gas grades but only one hose is used to dispense the gas. The shutoff valve is at the handle attached to the end of the hose and the hose is filled with whatever gas the previous customer selected. If you want to fill your gas can with only high grade gas then you need to first put about 3L of gas into your car in order to flush the hose. After that you can continue and fill up your gas can. It's a good idea to watch the volume count of the pump as it is often difficult to see how full the gas can is. I fill about 18L into a gas can rated for 20L in order to have a bigger pressure expansion buffer. Gas bought in winter contains the most amount of high volatile short chain molecules. It would pressurize your gas can a lot if you keep winter gas over the summer. It is a good idea to buy gas for long term storage in August, September or October.
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