Petrol fuel usage time

[Bronwen]

Hi - I’m trying to use the electrical mode as much as possible so I haven’t fuelled up for over 4 weeks. A friend told me that petrol can “ go off” and should be used, so in theory I shouldn’t be running electric with a full fuel tank but rather only 1/4 full fuel tank for “ emergency “ usage. Could anyone please confirm?
Thanks, Bronwen

 

[MG Clive]

It's true that fuel can go off, but I'd say that as long as you're filling up every 4 to 6 months, it will not be a problem. What you shouldn't do is use petrol that's been stored in a can for more than 6 months, always fill up with fresh fuel.

 

[decrep]

I was sceptical of this, but apparently the more volatile elements evaporate off. I thought a full tank would help, but I was told modern cars have a vented fuel tank, so it doesn't help. But I think fuel stored in a completely sealed full tank should be OK. BUT don't quote me on this

 

[mgpooter]

This thing about petrol going off I reckon stems from the older cars with carbies and their fuel pumps requiring the petrol cap to let air in (and out). That will spoil fuel over time and cause water to build up in these ethanol type fuels as damp air can get in and cause the volatile elements to escape.
The modern fuel cap is effectively sealed. You will hear the puff of air from a modern cap as you open it, so there is no problem with volatility loss or water ingress. Have always topped up myself, especially when it's cheaper, no problem.
With a classic car you can seal the cap using cling film over the winter when not used. A full tank also reduces the amount of air that can get in or out with temperature fluctuations.

 

[Archev]

This thing about petrol going off I reckon stems from the older cars with carbies and their fuel pumps requiring the petrol cap to let air in (and out). That will spoil fuel over time and cause water to build up in these ethanol type fuels as damp air can get in and cause the volatile elements to escape.
The modern fuel cap is effectively sealed. You will hear the puff of air from a modern cap as you open it, so there is no problem with volatility loss or water ingress. Have always topped up myself, especially when it's cheaper, no problem.
With a classic car you can seal the cap using cling film over the winter when not used. A full tank also reduces the amount of air that can get in or out with temperature fluctuations.

I’d agree with all that about petrol from what I’ve heard / read and personal experience. Diesel is notorious for attracting water - especially with boats moored for long periods.