So much wrong information in this thread. Drac, Dave and Dave are correct.
OP want less oil on your plane then run a lower oil content. instead of 18 try 16% oil.
IMO
Synthetic oil provides better protection when you keep your engine cool.
Castor protects better when the engine runs hot and you run it lean. Most MFG's suggest lots of oil to protect them and keep owner happy with their engines. If you're good at tuning an engine try a lower oil content and you might be surprised. Now one thing about oil content. If you lower the oil content and you see a drop in power it doesn't always mean that parts are rubbing and causing a power loss. On some engines the extra oil since it doesn't burn adds compression to the engine. So play around with the engines. try less oil and if you see a large drop in power try it with the head shim removed and see how it does then.