Many different types of natural gas such as gasoline and diesel fuel degrade after long enough periods of time. Typically three to six months and six to twelve months respectively. As such you may be wondering, does propane go bad? If so, how long will liquid propane fuel last by comparison along with how propane tanks affect the longevity of this natural gas.

Does Propane Go Bad?

Contrary to popular belief and what you’d expect based on how diesel fuel works a full propane/Liquefied Petroleum Gas (LPG) tank won’t ever expire. Due to this theoretically indefinite shelf life of propane, it can act as an excellent and dependable fuel source. For this reason, propane stored in gas bottles or another form of propane container will often be used to fuel portable stoves, emergency generators and barbeque grills.

Propane and LPG Shelf Life

The only limiting factor when you store propane tanks will be leakage from the gas tank itself. This means that whilst it doesn’t have the very limited shelf life of other natural gas variants the infinitely longer shelf life will ultimately mean very little if propane gas is stored improperly.

Does Propane Go Bad?

If Propane Fuel Doesn’t Expire Then Why Do Propane Tanks Have An Expiration Date? 

It is often the propane tank that leads to confusion and leads to the question of does propane expire or not. This is because many vessels that are used for storing propane such as propane tanks will have what looks like an expiry date printed on them.

So why is there a date then?

Well, the answer is simple. An expiry date isn’t used for the propane/LPG as it would for other fuel sources diesel fuel. Instead, this printed date is actually for the gas bottle or storage the propane is contained within or for the gauge on the tank.

The reason these dates are necessary is that whilst the propane/LPG won’t expire, a propane tank or indeed the tank’s valve will degrade over time. As such the infinitely longer shelf life of propane compared to other fuels may cause it to outlive its container. 

Some good news though is that the right containers will likely last quite a while. However, eventually, natural degradation of rubber seals or potentially a faulty safety relief valve can cause leaks.

As such, it is recommended that you have any propane tanks inspected by a professional on a somewhat regular basis. This will help reassure you that they are still in good shape, along with helping to ensure they are stored properly.

How Long Will Propane Burn?

How long the contents of your propane tank will burn for can vary depending on how it is being used. Certain tasks will require more propane at once whilst others may take longer to do but drain less propane gas per minute.

On average if grilling with an average-sized barbeque grill a twenty-pound tank should be good for roughly twenty hours. However, a larger, more thirsty grill may burn through the tank’s contents in about half as much time. These aren’t universal numbers of course but on average they can be a handy rule of thumb to remember.

Does Propane Go Bad?

How To Measure The Burn Rate Of A Propane Tank

To more accurately gauge how long a propane tank will last, you can also attempt to calculate its burn rate. This can be done by a professional, who will probably get a more accurate answer as the process is a bit complicated. 

However, it is possible to do this at home by yourself. For a good indication of how to calculate the burn rate of a propane tank, use the following steps:

  1. Figure out how much the actual tank itself weighs. This should be found somewhere on the tank itself. The tank’s weight is often known as the “tare weight”.
  2. Subtract the tare weight from that of the total weight of the tank plus the propane. This will give you the weight of your propane.
  3. Divide the total weight of propane by 4.24. This is done to understand the weight in gallons which simplifies things greatly. For reference, 4.24 pounds of propane is equivalent to one gallon of it.
  4. Check the burn rate of the appliance you will be using propane for. This should be denoted somewhere on either the appliance itself or any instructions it came with.
  5. Divide the total gallons of propane by the burn rate of the appliance. This will show you how long it would take that appliance to burn through the propane in the tank.

For a quick way of gauging roughly how much propane is left in your tank, the video below can be very helpful:

Can Propane Tanks Explode?

With many sources of fuel, there is always a concern about whether they will explode or implode. Naturally, for many, this is a concern with a propane tank as well. However, whilst it is potentially possible for a propane tank to explode, it is very unlikely that this will happen. 

Despite this though you should still be cautious with propane/LPG. This is because like with any other fuel source, explosions are still possible. As such, you should be vigilant of any leaks along with avoiding keeping it near to any sources of extreme heat.

Does Propane Go Bad?

How To Store Propane Safely

As mentioned above, you should always be conscious to keep propane tanks away from extreme heat sources along with watching for leaks. However, to ensure that your propane will be as safe as possible, there are a few other steps you should take when storing it.

Propane tanks are best kept in cool dry places. This will help to keep the propane/LPG within cool whilst preventing any rust from forming on the tank entirely. Ideally, this storage location should be below 120°F (roughly 50°C). 

Additionally, it is safer to keep propane tanks outside rather than inside. This is because indoor conditions are often warmer. Additionally, the consequences of a propane leak are potentially much worse when they happen indoors.

When stored outside, however, ensure that the area is dry and cover in a plastic coating to prevent rusting. Additionally, you should also ensure the tank is elevated slightly from the ground to keep it dry along with being level so it won’t topple over.

Final Thoughts – Does Propane Go Bad?

Despite what you’d expect based on knowledge of other fuel sources, propane or LPG as it is also known doesn’t expire. However, whilst the answer to does propane go bad is no, the same isn’t necessarily true for the propane tanks. This is because over time they can degrade which can cause propane to leak. As such they should be stored properly in level, dry and cool areas along with being regularly checked.

FAQs Relating To The Expiration Of Propane

Durability of Propane Gas and LPG Gas

Propane or Liquefied Petroleum Gas (LPG) as it’s also known is known for its ability to never go bad. As such it is very durable and reliable so long as it is contained in a manner that is appropriate such as in a gas canister or specialised propane tank. In fact, due to propane never going bad, you may end up having to replace the container for it before you do the gas if only used sparingly.

Is it Safe to Use a Full LPG Gas Cylinder Unused for Many Years?

The answer to this question can be either yes or no. Ultimately if the propane hasn’t leaked it will likely be safe to use. However, an issue could lie with the cylinder itself as it may have become damaged over that time. As such, it is recommended that even if the cylinder still looks fine that you should have it certified as being safe by a professional before using it.

Does Propane Evaporate In The Tank?

Whilst compressed in the tank propane won’t evaporate unless it is able to escape through a leak. However, if heated up to extreme temperatures the propane inside a tank may violently evaporate and cause the tank to explode.

Can You Use 10 Year Old Propane?

Since propane doesn’t expire it will be perfectly fine to use old propane. However, the container itself may make this hazardous as it could have deteriorated over time. As such, it is recommended that even if the cylinder still looks fine that you should have it certified as being safe by a professional before using it.

How can you tell when a propane tank is empty?

Outside of weighing the tank or using a gauge, there is a very simple way to tell how much propane is left in the tank. Simply get a large glass of hot water and pour it down the side of the tank. Immediately following which run your hand down where you poured the water. The moment you feel the temperature change from hot to cold will show you where the propane levels currently are. If you don’t feel this coldness, however, this means that the tank is empty.