If you don't like your OS .46 by all means run all synthetic in it. What are the %s of the blend you run in your four strokes? You should be running a castor blend in the Saito also. I use only WildCat Premiuom Extra which has an 18% 80/20 syn/castor blend. I use WildCat ProMix 20% nitro with 18% 95/5 syn/castor blend in my YSs, they love it..