Rotella T is on sale at Canadian Tire starting tomorrow. 25% off I think.
Why not? You can use different viscosities as you please... In fact most vehicles can use a wide range of oil types and viscosities... With a few exceptions, nothing is carved in stone... Now go scan through the big oil thread and you will see Rotella is one of the most popular oils (not sure where you've been hiding) of motorcyclists for the last decade or so....Why 15/40 instead of OEM recommended 10/40?
Actually, the T6 is fully synthetic...it is a 5w40. T5 is semi-synth is 10w30 and 10w40.Because it is full synthetic, meets motorcycle requirements and is cheaper than other alternatives.