All the above saying that 25:1 is the correct mix is incorrect!
25ml oil to every 1Litre of fuel = 40:1 ratio
-NOT 25:1 !
It is also dependant on the type of oil used.
When using manufacturers oil, it is usually 20ml to 1L (50:1) but when using 2T oil it is invariably 25ml to 1Litre = 40:1
Always check the info on the oil bottle -it will tell you the correct ratio.
JayC, November 2010