do I use 5w40 or 15w40?

[Degreaser]

What oil would be better in summer riding for my 2004 Kawasaki Vulcan 1500 cruiser 30K miles, Rotella T6 5w40 -or- Rotella conventional 15w40? I'm not wondering about synthetic vs conventional 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.

 

[bepperb]

The difference is less than you'd think. I switched to the 5-40 from the 15-40 thinking I'd have easier starting on the coldest rideable days (for me ~ 35 degrees). But, I wasn't blown away. They both seem to be good choices, personally I'd probably pay the extra just for the protection from overheat.

 

[rsnake]

I used to ride a Vulcan 1500 and have used both grades. Since the Vulcan is water cooled you really don't need a synthetic and I found that the Kawasaki "clunker" transmission really liked the Rotella 15-40 better. Save a couple of bucks and go with the conventional.