Engine oils......

[dr_fosg8]

The dealer giving you this "information" and if what you are saying is what they said ... NEEDS TO FIND ANOTHER LINE OF WORK!
are you sure they weren't talking about an energy conserving oil that has moly in it?

I have shell rotella-T 5w40 synthetic (blue jug) in my '82 gs850 now. the last oil change was with amsoil 20w50.

That very well could be, however they did say synthetics. If there is a specific kind of oil that is bad for the wet clutch I hope that is the oil they were referring to. However the same dealer wouldn't sell me NGK caps because they weren't the right ones, had to order them from suzuki(which I didn't do).

So synthetics are good as long as they are not energy conserving. Good info to have. I thank you Rustybronco.

[Nessism]

Oils labeled as Energy Conserving are always thin viscosity weights like 5W-30 and such, not 10W-40 like our bikes use. For this reason the worry is moot.

The advantage of synthetic oil is that it doesn't shear down as fast as dino oil (particularly cheap auto oil) so you can extend the change interval to offset the high cost. Synthetic oil also has better high temperature protection abilities since it's more viscosity stable. This is a nice safety feature but not overly important unless you ride your bike in killer summer heat at low speed where there is not much airflow over the engine. Other than these advantages, synthetic is no better than anything else. It's not more slippery, doesn't make your clutch slip, and doesn't protect any better than a high quality dino oil like Rotella.

All this said, my bike has synthetic oil in it and I've got a bunch more in storage (got a good deal at Kragen)

[rustybronco]

the oil change I did with amsoil 20w50 motorcycle oil was over 5,000 miles with little/no loss of shift quality.
that was a good reason to use it also.

so far 1,200 miles on the rotella-t 5w40... it felt a little hard finding neutral for the first 400-500 miles, but it's looking good so far.
time will tell.

go with nesissm's recommendation of rotella 15w40, it worked well for 2,000+ miles when I used it last.