Fuel storage in plastic drums....

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Originally Posted by Brian Hjelm

I was told long ago by a chemist from the Shell Co. that petrol starts to lose startability quite quickly and eventually will break down into a black thick semi-liquid as lighter components evaporate out. I had asked the question as I had an acquaintance at that time who was convinced that the nuclear holocaust, or at least an invasion by the yellow peril, was a real possibility and had set himself up with a near self-sufficient survival cottage in the dividing range. He was stockpiling petrol in steel drums.

Now I know there are plenty of stories of vehicles abandoned for years being started on the dregs in the tank, but the chemist was giving the professional opinion. How long will fuel take to break down? How long is a piece of string.

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If petrol is stored in a sealed impermeable container (steel should meet this condition, although even there the seal on the bung is permeable to some extent, although the area is very small, so for most purposes, it is negligible), then it will not lose the volatile fraction. However, the other effect that comes into play is the action of bacteria. This depends on the fuel being infected, something that can almost be guaranteed today, and critically the amount of water present. With no water present, no bacterial action, but it does not take much.

Hence, we can conclude that in tanks open to the air, life of fuel will depend on the volume of the tank, the temperature, the amount of ventilation, the humidity, the amount of free space, the daily or seasonal temperature variation (this moves air in and out of the free space, introducing more water and removing vapour), and in the case of sealed containers will depend on the amount of water present in the fuel and the temperature, as well as the container material.

The bottom line is that for practical purposes, the life of stored petrol is highly variable, although the above points suggest ways to improve it. Any figure quoted for life of stored petrol is probably going to be wrong in any particular case, possibly by a very large margin (either way!).

John

Interesting reading...

And pardon my ignorance, but does diesel have a "shelf life" as well?


There are selfish reasons for my question, but I dont want to take a risk (read: 1000 L of free diesel from a soon to be de-commissioned stand-by generator)

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Originally Posted by Basil135

Interesting reading...

And pardon my ignorance, but does diesel have a "shelf life" as well?

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Yes, but again it is highly variable. As the proportion of volatile hydrocarbons is much smaller than for petrol, evaporation is much less of a problem. However, since the density is much closer to that of water, it is a lot harder to keep free of water, and consequently bacterial action is more likely than with petrol. However, in general, diesel will last longer than petrol in storage - for years in a dry environment even in a ventilated tank, but if possible, avoid the bottom few inches and do not use it from a tank or other container that has been moved within the last 24 hours, so as to leave the water and bacterial sludge behind as far as possible.

John

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Originally Posted by Brian Hjelm

I was told long ago by a chemist from the Shell Co. that petrol starts to lose startability quite quickly and eventually will break down into a black thick semi-liquid as lighter components evaporate out. I had asked the question as I had an acquaintance at that time who was convinced that the nuclear holocaust, or at least an invasion by the yellow peril, was a real possibility and had set himself up with a near self-sufficient survival cottage in the dividing range. He was stockpiling petrol in steel drums.

Now I know there are plenty of stories of vehicles abandoned for years being started on the dregs in the tank, but the chemist was giving the professional opinion. How long will fuel take to break down? How long is a piece of string.

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Likewise, for those that race they shouldnt store fuel for any real time as the light fractions are also the top end power fractions that vapourise out. When you grack the jerry and hear the pssshhhhh come out... thats top end hp leaving the time. This is more of a problem with high octane fuels, but keep the fuels cool.

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Originally Posted by JDNSW

Yes, but again it is highly variable. As the proportion of volatile hydrocarbons is much smaller than for petrol, evaporation is much less of a problem. However, since the density is much closer to that of water, it is a lot harder to keep free of water, and consequently bacterial action is more likely than with petrol. However, in general, diesel will last longer than petrol in storage - for years in a dry environment even in a ventilated tank, but if possible, avoid the bottom few inches and do not use it from a tank or other container that has been moved within the last 24 hours, so as to leave the water and bacterial sludge behind as far as possible.

John

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Ther practice at GM-H was that all diesel trucks were filled to the brim as they came off line before being moved to yard storage. This was to limit condensation of water in the tanks from the movement of moist air in and out of the breather every day as the fuel heated and cooled. We used to invoice dealers for the full tank of fuel. Didn't they squeal.