Fuel filler cap

[StruanR]

What is the best material to make a sealing washer for a fuel filler cap?
Petrol is corrosive stuff nowadays.
I've cut them from rubber mudflap material (because I had that to hand), but that shrinks and goes hard.
Neoprene?
Would polythene washers be OK?
:confused:
Struan

[strat24v]

Nitrile rubber. Don't think Buna-n is up to it now. Ptfe is fuel safe but wether you can get it as a slightly soft sheet material, I do not know.

[ChrisCar6]

I use polythene washers and they seem to be unaffected.

[StruanR]

Thank you John, Chris, helpful as always.
:)
Struan

[StruanR]

Viton sheet seems to be the recommendation from suppliers now ....
:)