Same here. Changed to HKS synthetic rotary oil 10W40 at 1000km, now >2000km. Imperceptible oil consumption.
Most impressed with the clean oil on the dip stick every time I looked. I reckon rotary engine's lubrication circuit is cleaner because there are no valves, cams, camshafts, rockers, rods, reciprocating mechanisms in the crankcase, etc.
Bought Aug 2003, Sold July 2007 : JDM Pearl White RX8 250PS Type S 6MT, black leather, factory fitted rear fog light, Carbing front brace/brake stopper, Whiteline F&R solid sways