In a good condition RB25 I HIGHLY recommend Fuchs 10w30, Bursons stock it, Have been running it in the Stagea for 40k km, motor is cleaner, smoother, more economical than when i first got it, i have run motul once, wasnt a fan.
Their 10w40 is another option. Motul 300v I understand, but the lower end stuff I dont get the hype. Chuckie has had his oil regularly tested up to 20k km and the fuchs doesn't deteriorate.