Lee,

Man you talk funny, "mate" "petrol", you need to come north a bit and learn real English. Just kidding, my wife and I enjoyed our two weeks in Australia. Sorry I can't exactly answer your question because the tube of silicone is up in Minnesota and I won't be back there until early May. I thought all silicones were impervious to gas. The stuff I've used is blue in color, and I believe it is advertised as a gasket material used in car engines. I hope this helps a little.

G'day
Chuck