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With T-6 my viscosity was 90% of minimum spec at 2000 miles.About 88% of min at 4000miles.
Can't find the 15/40 right now but it was about min spec for viscosity at 4000 miles and engine sounds better and less gear whine than T6.
Blackstone lab tech told me that according to All there FJR records oil sheared to below min spec(spec being viscosity range of new oil)in 90% of cases. They would not say which" brand" stayed in spec (the 10%) but , did say that 10-40 was THE worst for shearing.
I believe 15/40 is the thinnest that should be used (unless running real cold weather and starts). I may also do a 20/50 test. (Blackstone hinted that this viscosity was the 10% that stayed closest to in spec).
I know any oil will fare okay but it all made me curious when the recommended 10-40 wouldn't hold spec either.
The bevel drive causes much more shearing of engine oil than would be experienced in chain drive bike.
Can't find the 15/40 right now but it was about min spec for viscosity at 4000 miles and engine sounds better and less gear whine than T6.
Blackstone lab tech told me that according to All there FJR records oil sheared to below min spec(spec being viscosity range of new oil)in 90% of cases. They would not say which" brand" stayed in spec (the 10%) but , did say that 10-40 was THE worst for shearing.
I believe 15/40 is the thinnest that should be used (unless running real cold weather and starts). I may also do a 20/50 test. (Blackstone hinted that this viscosity was the 10% that stayed closest to in spec).
I know any oil will fare okay but it all made me curious when the recommended 10-40 wouldn't hold spec either.
The bevel drive causes much more shearing of engine oil than would be experienced in chain drive bike.