if it were my own i would use the recomended oil, as for who i work for....they have been using 15w40 for 10 years now. Our 2 cylinder kawi's dont mind it at all, average 2800-3200 hours before most of the engines start burning, or leaking oil. as for the smaller engines i would definately use the lighter reccomended oils since they are mostly splash lubricated whereas the bigger engines are usually pressure lubricated. Grant you they change their oil and filter every 100 hrs since the day they were purchased, 2 times a month sometimes in the early summer. This is just normal everyday 15w40 i'm talking about...Rotella is much better from what i've heard over the years
nevertheless, if it isnt the engine's recomended oil, it will void all warranties of the engine. And they can tell fairly quickly what grade oil was used if they feel like diggin into it. It all comes down to opinion... climate, usage, frenquency of service to engine are the main contributors to a long lasting engine...oh and a compitant operator lol
I'd wait a week or so on this thread and let everyone comment on what they have seen over the years and draw your own conclusion for i am by far no expert on oils.
