Apparently switching from synthetic to mineral back when synthetics first came out was a big no no for they were incompatible. With current oil technology, replacing one with another is no big deal.
It's my understanding that you want to find a brand/type of oil, and stick with it. Each manufacturer develops their oil with specific additive packages to help maintain your engine. By constantly switching brands, any long term benefits derived from these specific formulas are reduced.
Here's a forum dedicated solely to oil: LINK.

 

There was another story about an agency in Louisian that dug up some Glocks that were submerged in salt water for a real long time. They were able to clean them up and use them again. I've got a G37 & G39 myself

 

The rotella conventional oil is fine, but most use the syn because it is just a couple bucks more. Look around and you should find it fairly easy at a truck stop, different wally world, auto store. Or just use regular.

In the area of glock I have a 19. The use and abuse test are neat, but most modern guns could handle them. Mostly hype but fun to see. I have never had a single problem with it, but I have never had issues with my s&w 629 .44 mag either. I carry my 19 as it is more practical.

 

Yeah, it's like "are you happy to see me or is that a 629 in your pocket", lol.
Nothing like a good quality wheeler

 

No doubt, people say "but it only has six bullets"...I say if I need to use all six, then the 629 will take care of the rest. You get knocked up side the head with it and you know it.