Originally Posted By: tc1446
Originally Posted By: alarmguy
Yup, you will always be better off with a 15/40 over a 5/40 in a shared sump bike, there is a reason bike makers dont suggest a 5/40 oil and its all in the UOAs on this forum.
Other than BRP who sells their 5-40 to Spyder owners and claim its good for
9300 miles between changes. Their Rotax motors are all shared sump. FWIW, a
couple years ago I ran some Rotella T 15-40 conventional oil and a UAO at
3000 miles showed to be down in mid-upper 30 weight. I've never run anything
over 5000mi but BRP claims that the shearing rapidly tapers off, so you can
do the long UAO's. Being old school, I'm sticking with a good synthetic and
changing at 5K.
Exactly, all oil in shared sumps shears rapidly in the first couple thousand miles then levels off.
Since the maker of your Spyder recommends a 5/40 they are aware of this and are quite happy with the engine/transmission running 30 weight oil. Really simple stuff.
For bikes that recommend 10/40 ..
15/40 oil will shear less, then the 5/40 Rotella and many people with metric bikes might notice that shearing using 5/40 experience less then smooth shifting.
If you change oil regularly like you do at 5000 miles (and me at around 3000 or so) it doesnt matter what you use as long as it is within specs from the manufacturer. I use conventional oil but syn is fine.
