What oil would be better in summer riding for my 2004 Kawasaki Vulcan 1500 cruiser 30K miles, Rotella T6 5w40 -or- Rotella dino 15w40? I'm not wondering about synthetic vs dino oil but mainly the weight. Temperature here in summer Nova Scotia is not hot but moderate and my vulcan is water cooled. I am guessing I would OCI the oil at 3000 miles. Recommendations please.