Before I kick this article off I have to give credit to Off the Grid News; which, after going through a fair number of webistes, provided great detailed information on fuel longevity.
Right now in my little apocalypse shelter I have a diesel generator and several jerry cans with fuel; all of which I’m sure is bad by now. But it gave me some curiosity about fuel longevity and storage. The concept first caught my eye while reading Patriots by James Wesley Rawles.
The fact is gasoline and diesel will degrade over time. That can lead to a number of problems, ranging from hard starting, to rough running, to no starting at all. And just like food storage, there is not perfect chart of how long fuel lasts because there are too many contributing factors.
Fuel is broken down into two main categories for our purposes. Although there are many types of fuel oils, we care mainly about gasoline and diesel. These are far and away the most common fuels, fuels that we will desperately need during survival situations to power most anything.
Number two diesel is a fuel oil that undergoes a relatively low level of refinement. As such, it is very stable, and its stability means that it will last the longest. Even without treating it, diesel fuel will last for a year with no problems at all. It’s just an inherently stable product. When treated with fuel stabilizer, the life of diesel fuel can be extended beyond five years.
Unlike diesel, gasoline is a highly refined substance with complex molecular bonds, which means that over time, these bonds break and the fuel reverts back to an earlier, unusable state. One characteristic of gas is volatility, a term used to describe how easily and under what conditions the gas vaporizes so it can be efficiently burned in your car’s engine. Gasoline comes in three main grades at the gas pump categorized by the octane rating. Octane is the “punch” that provides the energy for internal combustion. The higher the octane rating, the hotter the fuel burns, meaning the more power generated to drive the engine. In the United States, octane generally starts at 87 which is regular, then 89 which is mid-grade, and finally 91 which is super or premium. Some individual states may have higher or lower octane ratings available for sale, but those are the averages.
The most highly volatile components in gasoline also tend to evaporate over time. As they do, the remaining fuel’s volatility and ability to combust properly degrades. The less volatile the fuel, the less effectively it burns in your engine. The result is diminished engine performance. Your engine may still start and run, but it probably won’t run as well.
Hydrocarbons in the gas react with oxygen to produce new compounds that eventually change the chemical composition of the fuel. This leads to gum and varnish deposits in the fuel system.
Generally speaking, the problem with gasoline over time is that as the molecular bonds break, the octane rating falls to the point where the gasoline is no longer able to produce the energy required for effective internal combustion. Some devices, like two-stroke generators, don’t need octane rich fuel. Others, like modern car engines, will knock badly with even a slight reduction in fuel quality. What this means to you is that the clock is ticking on gasoline – it’s degrading right now in the fuel tank of your car. It’s not unusual for highly refined premium gasoline to lose significant amounts of octane within even 90 days, and low grade gasoline to lose octane within 6 months. If you are intent on preserving fuel, then use gasoline stabilizer such as Sta-Bil, which slows the rate of chemical bond breakdown, giving you up to a couple of years of life increase on your gasoline.
Sta-Bil is not recommended in ethanol blended fuels as it causes a chemical reaction corroding brass in carburetors and speeds up the process at which ethanol mix gas breaks down fuel lines in vehicles made 2006 or older. All auto gasoline in the US contains a 10% ethanol mix as of 2007.
Ethanol fuel blends have a shelf life of only 90-100 days, under ideal environmental conditions.
When exposed to water, E10 gas will contaminate and should be discarded. Only 1 tablespoon of water/per gallon will cause fuel to contaminate/separate.
Both fuels should be stored in a cool, dark place, and should be in topped-up containers with as little airspace as possible. Lastly, treat your fuel before you store it – fuel additives are rarely capable of bringing dead fuel back to life, but they will extend the life of new fuel significantly.
It’s hard to know how old the gas you just bought actually is. It may be fresh from the refinery, or it may be a month old already by the time you top off your tank. Some gasoline is mixed with better or more oxidation inhibitors than others.
The ideal way to keep gasoline most fresh over a long period of time is in an air tight container.
Compare stored gasoline with fresh gas. If you notice it is darker or smells sour it is probably bad.
Condensation can form inside your gas tank and lines from heat cycling. Fuels such as E85, which have a high concentration of ethanol alcohol, may be even more susceptible to water contamination, as ethanol likes to draw moisture out of the surrounding air.
Water contamination can be a problem at gas stations with light traffic due to a slightly different kind of heat cycling. The underground storage tanks experience increases and decreases in temperature. This can cause moisture to form and contaminate the fuel. When you fill up at such a station, you’re pumping in the water along with the gas. Such low-traffic stations may also have other contaminants in their underground storage tanks, such as rust. They are best avoided when possible.
Water, of course, does not work too well as a fuel in an internal combustion engine. It will cause hard starting and rough running until it’s purged from the system. It can also contribute to internal rusting of the gas lines and tank. The resultant scale and small particles can create a true nightmare, sometimes requiring the replacement of the gas lines and tank at considerable expense.
According to the Sta-Bil website it will keep fuel fresh for an additional 6 to 12 months when mixed into fresh gasoline. Doubling the dosage will keep fuel fresh for up to 2 years.
This is one of the most well-known fuel preservers utilized among prepping communities, but there are others that perform just as well.
Here is part of a comment in response to an article on Survival Blog that caught my eye:
“The product STA-BIL that you reference in your writing, will, in fact, stabilize gasoline and diesel fuel. But bear in mind this is a “consumer” type product – designed with strength only sufficient to extend fuel life 6-to-12 months. The active ingredient in this product is actually in a very small concentration.
We manufacturer PRI-D and PRI-G for diesel and gasoline respectively. While we largely sell these products to the industrial market, we also have made them available to recreational boaters and RV enthusiasts through several hundred outlets nationwide. The chemistry we offer in our consumer package is in the same strength we provide to industrial users – users that include nuclear power facilities, and countless thousands of entities that store fuel for emergency power generation. These products have also found a popular following among those of us in the “prepper” community. On average, one dosage will keep fuel fresh for about five years – sometimes much longer. We have had some fuels in storage as long as 12 years – and they are still refinery fresh. As a side note – even kerosene for lamp oil can deteriorate, so it is also of critical importance to treat these fuels as well.”