I've used both brands in ur original post liked castrol better Yamaha R-2 s gd Amsoil s the best but pricey I've heard gd things about Lucas 2 cycle oil FYI always use synthetic or synthetic blend.i heard royal purple mite be gd so wen u find an oil u like its best to stik with it also run premium fuel better results.jst remember Valvoline s been around over 100 yrs an it's all I use for automobiles any way.awesum results btw .