Hello all,
I use a fully synthetic oil by exol which is an English company who blend their own. When i found their oil i contacted them and asked if it was on par with tts to which they sent me a reply saying that the additives in both oils after checking the tts oil spreadsheet was.
Also when you consider that our engines are hardley high revving compared with two stroke motorcycles, but that said you want to give it the best, i would stick with fully synthetic.
The best bit is if you buy their fully synthetic in a 25 litre drum which i did being a Yorkshire man and buy a tap screw for the top myself and others who fly with me can now have a litre of oil for £4, a considerable saving on £12.
Google exol oils to get the details, Alan.