Who is familiar with these oils ?? My motorcycle engine ( KAWA VN 900 ) is filled with 10W40 on the factory side.Now I have for a long time the feeling that this 10W40 does not necessarily meet the requirements of motor, clutch and transmission.The clutch slips from time to time and the transmission makes noises.To this end, I pass through a zone of 30 in the 2nd passage, the motor gets hot (fan jumps on ).I now thought that it might be on the oil, since it is a cooling end. It should have a higher load (upper temperature range ). Can I just do the oil in this way, would there be an improvement in terms of clutch, gearbox and engine or should I stay with the 10W40 better? Technically, according to Kawawerkstatt everything is OK with engine/coupling/gear. Drive my Vn only with nice W For bad weather, my KLR 600 keeps the nose in the wind.