I consider the choices & have always used good oils.
In the early 70’s I started using Filtrate & have witnessed the progression from mineral oils through to synthetics. As a consequence, like many others, I tried the oils that were supposedly ‘superior’ in one way or another, such as Bel-Ray & Castrol R.
Nonetheless, for probably a couple of decades, the oil of choice has been a full synthetic, for road or race.
Bearing in mind the nature of, say, a Group Four with no fan cooling, that is absolutely caned on track, I would say that good fully synthetic oils such as Morris’s, Putoline & Rock are all fairly similar & worked well @ 3%.
In 2012, my local Exol branch gave me five litres to try on track, but I was sceptical & took the softer option of using an oil that other riders relied upon. So, what would you do with five litres of a fully synthetic oil, specific to air cooled two strokes?
Tentatively, I used some in tuned road engines, but was alarmed by the smoke produced, though happy with the look of the internals when stripped down.
Dropping the mix to 2% in 240cc plus cast iron bores & stroked, tuned TS engines has not caused any issue. No rings sticking, excess carbon or piston varnishing has been in evidence, & the TS engine is ridden hard constantly. However, the engines I speak of comprise the optimum squish, bore clearances & are jetted well, which is more than many can claim.
(Then again, nor are these engines laboured in high gears during the running in process, which many clearly fail to understand as they plod their engines along thus suffering minimal fan cooling. To make matters worse, they add MORE oil consequently weakening the fuel/air mixture!)
I’ll step down from my high horse now.
Five litres for fifteen quid (cash) of a fully synthetic race oil that is specifically for air cooled engines & can be utilised safely in leaner oil/fuel mixes? No brainer IMO……
