Stuck clutch - oil issue?

[eldevigo]

I have a cranky '83 GS1100E which I haven't ridden much because it's having starting issues. The last time I rode it, I went about a mile across city surface streets to move it from my previous home to the place I'm living now. This was about two months ago.
Some time after that ride, the clutch pack froze up real good. It won't disengage now when I pull the clutch lever, which was not an issue at all when I rode it to the new house.
I tried clamping the clutch lever for a few days, no luck getting it to pop free.

I see a number of long-timers here recommend Shell Rotella T4 oil (15w-40?). The last time I changed the oil in this bike (last year) I put in Chevron Delo 15w40 (this stuff).
I also see people saying that slippage and other additive-related issues is not a problem with 40-weight oils, so I'm not sure if this is something I should be concerned about.
I don't remember feeling any slippage in the clutch on the drive over here, but it was a fairly short trip and I wasn't going very fast. I'm not sure what else might cause the plates to stick this bad on such a short drive however.

1. I'm currently draining the engine do to some other work, so if I need to get rid of the Delo I guess now would be the time to do it. Should I spend the money? Never mind about this one, I remembered there's some other mystery oil in there too so I'm just going to do it.
2. I've also seen a comment about aftermarket clutch springs being a source of potential issues. Any tips on how to tell whether the PO put aftermarket springs in or if they're OEM?
3. On a related topic, any tips for physically freeing the plates in a frozen pack without damaging them? I'm thinking of putting them edge-on on a wooden block and whacking them lightly with a dead-blow hammer, does this seem like a bad idea?

Thanks y'all

[eldevigo]

Actually I just recalled that last fall I had a mechanic look at the bike. I'd forgotten that I had left the oil low when I delivered it so he topped it up, and I have no idea what he used, so the oil I just drained out is probably a substantial mix of who knows what... I think I'm gonna just change it out to be sure, so never mind about the oil question.
I am still interested to hear any feedback on the other two questions though!

[Nessism]

Oil won't cause the clutch to lock up. Something is going on with the release mechanism, or the outer basket is notched up really bad and the plates won't move freely. Sounds like time to remove the cover and inspect everything.

[eldevigo]

Alright, will do! I'm planning to remove the pack anyway to try to knock them loose with a plastic mallet, I'll look over the springs, basket, release mechanism etc. while I'm in there. Thanks!

[rphillips]

Think improper oil or oil additives can cause slipping, but never heard of it causing clutch sticking. I've seen them kind'f stick a little but nothing like you're say'in. Just old country folk advice, A stretched or almost broke cable can contribute to this. Tighten the cable till there's no slack, even a little tighter if you can, that'd get all the movement of the pressure plate you can get and see if that helps. Little arm on clutch cover should be just slightly outside of parallel with clutch cover gasket to get full motion of pressure plate. Like freeing a stuck eng. sit on bike, wheels on ground, put it in gear, and with clutch pulled in, rock it back and forth, possibly freeing a couple or few of the plates. Just me thinking if you get it to disengage at all, it'll get better with a little running.

[dgates1]

Perhaps it was slipping on your last ride and overheated.. causing plates to warp?? Agree with Ed to take a look inside if it is not related to your clutch cable.