I've been using Rotella 5-40 synthetic in my Kawasaki EX500 for about 11K miles with success, changing about every 3K along with a new filter. The transmission has always been a little crunchy if I'm not careful with my shifts, and based upon what I've read here a lot of folks think the dino Rotella 15-40 resists shear better. It would also be nice to save a few bucks. Are there any disadvantages to going back to a dino oil? How about starting issues when the temperatures drop to the 30s (I still ride if it's above freezing)?