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I used Rotella non synthetic 15w-40 T4 without issues. It's JASO MA/MA2 certified. Honda did not stipulate that synthetic oil was required and, IMHO, you don't really need synthetic for a bike designed in the late 80's. Purchased by the 18.9 L pail for about $60.
T6, fully synthetic is good as well, at least twice the cost. I think T6 is probably a better oil than the T4, but having said this, many thousands of people have run the 1100 on T4 for millions of miles without issue. I don't remember ever hearing anywhere that synthetic oils might not be good for an older motorcycle with a wet clutch and I certainly don't remember any forum member posting any issues related to the use of Rotella T4.
T5, synthetic blend is not JASO MA, MA2 certified, so I wouldn't use it.
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T6, fully synthetic is good as well, at least twice the cost. I think T6 is probably a better oil than the T4, but having said this, many thousands of people have run the 1100 on T4 for millions of miles without issue. I don't remember ever hearing anywhere that synthetic oils might not be good for an older motorcycle with a wet clutch and I certainly don't remember any forum member posting any issues related to the use of Rotella T4.
T5, synthetic blend is not JASO MA, MA2 certified, so I wouldn't use it.

Full Synthetic and Synthetic Blend Oil Products | Shell Rotella®
View the Shell Rotella line of full synthetic and synthetic blend oils, providing protection against wear, deposits and oil breakdown, with enhancements in temperature performance.