Fuel Storage

With the recent Colonial Pipeline spill causing problems with fuel supply in several states, a member of our Facebook page asked about storing fuel. To our surprise, this is a topic that we hadn't covered yet.

Most of the “experts” recommend storing enough fuel for your vehicles to make it to your BOL plus 50%, and enough for your generators to run for at least 24 hours. I rarely ever let my vehicles get below a half tank of fuel (that's three round trips to the BOL), and what I have on hand will run my generator a lot longer than 24 hours. Use your own judgment on how much you need to store.

Storing fuel for your vehicles and generators breaks down into two parts: safety and treatment.

Safety

• Never store gasoline inside an inhabited building! Gasoline is more volatile than diesel, and the vapors are heavier than air so they can travel along a floor to an ignition source. A fan motor starting, a pilot light on a water heater, or a light switch being flipped can cause a huge explosion.
• Keeping air away from the fuel is the first step to storage. Containers must be airtight, preferably without a separate vent hole to reduce the chances of air getting inside and vapors getting out.
• Fuel containers are color-coded: Red for gasoline, yellow for diesel, blue for kerosene. Don't mix them up unless you want to destroy an engine or two.
• Metal containers are better than plastic. Metal seals better and is more durable than plastic, but it costs more.
• Have fire extinguishers close to anywhere you are storing fuel. You're not likely to be able to put out a fuel fire, but you might be able to prevent a small fire from reaching your supply.
• Keeping the fuel cool and at a constant temperature is the best way to store it. You're not going to be able to store gasoline below its vapor (or flash) point (-77° F), but you'll reduce the condensation inside the containers. Diesel,with a flash point around 105° F, is a lot easier to store. 
• Minimizing vapors means less of a chance of accidental fires and explosions.
• Large containers (over 5 gallons) are easier to deal with safely than small ones. Having a 55 gallon drum or 100 gallon transfer tank leads to fewer vents and spills. It is also easier to keep track of when it is time to rotate your fuel when it is all in one place.
• Transfer tanks and pumps are designed to be carried in the back of a pickup and have stringent DOT and other government regulations. Be careful if the rule of law is still operating, and do your research; I have a CDL with a Haz-Mat endorsement so I can get away with a bit more than most people, but it comes at a cost.

Treatment

There are several products on the market for treating fuel for storage, and even more anecdotal evidence about which of them is the best. Improving the thermal stability of the fuel seems to be the main goal, meaning that the treatments are trying to keep the fuel from breaking down when warm. Avoiding ethanol blends seems to be a common starting point, due to the alcohol's affinity for water. I have researched a few and come to these conclusions.

• Sta-Bil is the most common, and will work for a gasoline stored for up to a year. Re-treating every year seems to maintain the stability of the fuel for several (up to an indeterminate number of) years. I've used Sta-Bil in my lawnmower gas for years and have never had it go bad over a winter, so I can testify to at least 8 months of effectiveness.
• Sea-Foam is more of a cleaner than a stabilizer, but it will help refresh old gasoline that wasn't treated and provides some protection for stored gasoline. The marine grade gets better reviews than the standard grade.
• Several 2-stroke oils have stabilizers added. From what I've found, they seem to work as well as Sta-Bil.
• PRI makes PRI-D for diesel and PRI-G for gasoline. They are industrial suppliers that specialize in fuel treatment for marine and heavy industrial customers, so their retail footprint is small. Their products are in use in large ocean-going vessels and fuel tanks for back-up generators at nuclear power plants, something I consider a good endorsement of their efficiency. The bottles are more expensive but treat a lot more fuel, so compare unit prices before buying.
• There are several “enzyme” treatments that claim to be able to revitalize stale gasoline, but the jury is still out on how effective they are. Anecdotal evidence becomes “He said, she said” before the truth is ever known. Several of these products haven't been on the market long enough to back the claims they make, which tends to raise the reading on my BS meter.

Long-Term Storage
Gasoline and diesel are not designed to be stored long-term.

Freshness

• As sold at the pump, gas is going to stay “fresh” for about six months and diesel for about a year. 
• Both will slowly oxidize from contact with the air and lose their combustibility. 
• Both will absorb moisture from the air if they are exposed to it. Ethanol-blend gasoline is worse in this regard.

Moisture

• Water is denser than diesel or gasoline and will settle to the bottom of any container. 
• Water in diesel leads to biological growth of bacteria that will foul filters and block lines.

Fouling

• Diesel tends to form gummy deposits that will plug filters and injectors.
• Gasoline will also form gums and varnish that will plug a carburetor and injectors after storage.
• Both will cause carbon (soot) build-up inside an engine after sitting for a long time, which reduces an engine's power and makes it run rough.

My Setup

I heat my house with an oil-burning furnace. Fuel oil is nothing more than low-grade diesel fuel, so I have dealt with storing up to 500 gallons of it at a time for the last 20 years. My tank gets refilled at least once a year, so I have had no reason to add a stabilizer to it, although I have started adding an antibacterial treatment to keep the sludge growth down, as filters are a mess to change and I hate having to prime the fuel pump on the furnace to get the air out of the line. 

Since the engine in my M35A2 truck is a multi-fuel diesel, it will burn fuel oil just fine. The diesel tractor runs on #2 diesel already, so using fuel oil won't be a problem with it. My furnace fuel tank is my back-up truck fuel tank, although the DOT will get pissy if they catch me using dyed fuel in a vehicle on the road. (The dye is added to indicate that no road taxes were charged when the fuel was sold.)

I keep a few 5 gallon cans of gas on hand for emergencies and rotate them through the lawnmower and chainsaws. I have used Sta-Bil for years and never had a problem, but it rarely sits for more than a year. It seems like I'm always running into someone who has run out of gas, or some other need pops up, and the stored gasoline gets used and replaced before the year is up.

Use common sense and the best information you can find when trying to store fuel for an emergency, and you should be fine. Never forget that you're working with something that is designed to burn or explode, and give it the respect that it is due.