On 21/08/2015 13:29, Martin Brown wrote:
On 21/08/2015 13:08, Rod Speed wrote:


"Brian-Gaff" wrote in message
...
I heard a talking head the other day saying that as supermarket fuel
is bought on something called the spot market, it can vary, and is
often quite old and thus its octane value can be depleted.

Perhaps someone can tell me how old fuel loses its octane value?

The more volatile components evaporate off faster.

It isn't just that. Many modern fuel mixes are slightly hygroscopic and
once there is some water in it various esters can form. The upshot is
that old fuel does not evaporate to leave absolutely no residue.

The ethanol content is particularly problematic in this respect.

Storage of fuel surely has to be nailed by now.

It isn't necessarily economically viable to store
it like that with the cheapest spot market crap.

Even with stabilisers longer term you would need to keep it sealed under
nitrogen to prevent gradual slow oxidation of certain components -
especially when stored in a rusty steel tank.

Most of the stuff you find on the web about long term fuel storage is
written by deranged survivalists who are nutty as fruit cakes.


Well put!