get a semi synthetic oil 10/40 but it wont solve the problem chances are the clutch basket is worn or the steel plates are warped slightly which causes the drag if you sit at traffic lights with the clutch pulled in and in gear it will get worse as the heat genarated by the drag will cause the plates to expand and drag more my clutch basket is worn badly from hard starts its the tabs on the clutch plates that cause notches in the basket and the plates dont release properly i stripped mine and smoothed the notches out but still doing it just not as bad i will be putting new steal plates in plus a new friction plates which will sort the problem out altogether the only way to check to see which of the two it is, is to strip and inspect just hope your not unlucky like me and its both!!!!