I changed the oil on my '89 Kawasaki 454 LTD motorcycle yesterday. I put Mobil 1 5w40 synthetic oil which is a little controversial. The problem is some synthetic oils aren't okay for use with wet clutches like motorcycles have. So you switch to that oil and uh oh, now the clutch slips and you can't go anywhere.
The magic seems to be "energy conserving" on the oil label. Theres a circle brassard kind of thing on the back of the oil bottle which would have the words "energy conserving". The 5w40 I use in my car doesn't have that so I figure its okay.
The 5w40 thing scares people too. I've been using 10w40 for the 4 years I've had bikes, its pretty much the standard for Jap bikes. So plenty of people are telling me I need to use Mobil 1 15w50 since thats "better" than 5w40.
I don't want to get into get into a big discussion of oil weights and all that foolishness right now. Lets leave it at from what I understand about oil weights 5w40 should protect my bike at least as well as 10w40 when its hot and better when its cold since it should be lighter when its cold and should thus flow better.
Anyway I swapped in the 5w40 yesterday (burned myself removing the old oil filter) and took the bike for about a 5 mile ride during which... nothing happened. Nothing bad anyway, the clutch seems just the same as it was, the bike shifts fine, nothing bad at all. Thats sort of the downside with this, you do a change fraught with controversy and then nothing exciting happens, which is good but sort of a downer....