Thanks very much Crosbyman and Tubs for your replies……..I never thought of using fully synthetic oil,although I use semi synthetic in my car.
I have been using Valvoline 2 stroke outboard synthetic enhanced marine oil, NMMA TC-W3 and currently have over 20 litres stored in my workshop.I presume the word ‘enhanced’ means ‘semi’
After receiving your replies I contacted the two major sources of oil here in NZ and was told that they only carried fully synthetic 2 Stroke for motorbikes (air cooled motors) and not for outboards(water cooled), so it looks like I will have to carry on using up my existing stock at this stage.

In doing so, what ratio would you suggest……..a 1/4 pint per gallon (1 to 32) or 1/3 pint per gallon (1 to 24)?
Interesting to note that there is no mention of biodegradable on my Valvoline containers.

I watched your U tubes and was very surprised that you only use 3oz of oil per gallon !

Thanks once again.
MonteNZ