Many thanks for the detailed description.
The OP stated that
Petrol does not keep/stay fresh like it used to. I had a whole heap of problems
I was advised to only have as much as I use in a day.....
Petrol apparently absorbs water from damp air (dont ask me how)
Your post explains why water is absorbed. However I think the question has to be 'by how much'. If it really mucks up engines if left in the tank for too long .....what is 'too long?' .....then surely we'd be forever topping up the petrol in our cars to minimise the amount of water vapour. In reality, I think it has more to do with the ethanol mucking up the seals in the carburetors on some engines. Ergo E5 = less ethanol which must be a good thing.
I'm no chemist nor do I know much about the additives ethanol aside in regular fuel however... -
I've owned a Honda Izy lawnmower bought new maybe 10y ago and after a couple of winters it developed an issue whereby after warming up and coming off automatic choke the engine would constantly hunt, but still work.
My days of tinkering with engines are long past and I took it to a local lawn mower service place for repair and one week later picked it up after parting with >50% the cost of the original mower and it ran fine, until after the following winter...
The 'shop had fixed it by cooking the carburettor in a solvent filled ultrasonic bath and I deduce that these models are prone to blocked idle jets because they have such small ~160cc engines and are reasonably fuel efficient and hence the idle jets are tiny.
Some searches online show this is a common problem and usually resolved by thorough cleaning with carburettor cleaner and aided by the use of a fuel additive - Briggs & Stratton make a commonly available one, that diminishes the tendency of the ethanol to separate out of the fuel if left undisturbed for months..
Subsequently I have used this in the mower and have had no further carburation issues.
There are also lots of info on the web as to how to remove the ethanol from fuel, I deduce by owners of historic vehicles that cannot run on E10 fuel, bizarrely this is done by adding water to the fuel and agitating it since the ethanol has a greater affinity to water than petrol and will dissolve out into it.
Since water is denser than petrol it ends up at the bottom of the container, and some techniques use water soluble dyes to aid visually eye-balling the separated fraction.
Gawd knows what else is leached out in this process nor what affect this has on the octane of the residual fuel but it seems to be a popular pastime for some folk....
wrt solubility, E10 means 10% of the fuel is ethanol and ballpark petrol absorbs water at ~1% by volume....