On Fri, 09 Oct 2015 09:44:15 +0100, T i m wrote:

What is the best and safest way to dispose of the old petrol?

As long as it's clean I can't see any reason why you wouldn't use it in
a petrol car, especially an older one with no fancy cat or electronics.
I'd happily use it in the kit car on top of a (at least)
half full tank. ;-)

Given that we're talking mostly about two-smokes, it can be taken as read
that it isn't "clean". I did once tip about three or four litres of
slightly over-oily and long-since premixed two-smoke into the near-full
25l tank of one of the 2cvs. Never again. It pinked like an absolute
bugger.