To answer Prigal, the G20/2300 will be destroyed if you a low-oil fuel, so I likely meant to say "clearances" and not "tolerances" above. The S-2000, S-2500, S-3000, G-3250, and G-4500 need to be run on fuel that's 12%-15% oil until they are well broken-in, and then fuel with an oil content of 10%-12% can be used. SuperTigre recommended that the oil be 100% castor oil in all cases. That's how they designed the engines.
So it would be safe to assume that since the engine was designed for castor oil lubrication and most commercially available fuels have very little castor oil in the fuel (if any) that the user should be using a higher oil content fuel in these big Tigres than is prescribed if the user's fuel is mostly synthetic oil? I'd think so.