Hi Guys,
Some information which is probably just going to add to the confusion
In the past two months, two 503's from the club I where fly from, had their rings stick in the pistons, resulting in loss of compression.
Both of them were taken to Solo Wings where they were repaired, and the advice which they were given was to stay away from chain saw oil because, unless your prop is under pitched, your engine should not reach 13 000rpm
These engines had both been run on chain saw oil, the recommendation from Dave Miller was to use Castrol superT or 2T cannot recall exactly.
Only passing this on because of my great respect for Dave Miller and his experience and knowledge, and in the hope that it prevents someone elso going through the same unecessary experience / cost