I don't think anything will happen. I work at a jiffy lube and people come in(alot of regulars) who always switch back and fourth from our conventional, synthetic blend, and full synthetic with no problems.

 

The OP's complaint is truly just an irritation but after reading other horror stories on the forum, I'm definetly going to change all my own fluids.
Jiffy-Lube's well publicised FkUp's recently has confirmed to me that even a simple oil change cannot automatically be counted as a job well done when there is no way you can know exactly what they did.
I think most are honest but can you ever be sure that you got exactly 5qts of fresh oil ? New filter? A specified brand? In almost every case, no.
DIY, save some bucks and enjoy a great peace of mind.

 

As long as it is 10w-30, you are fine. These days decent quality "dino oil" is pretty hard to tell apart from full synthetic anyway. The business about not switching back and forth is ancient history, and mostly myth to boot.

 

Not everyone is in a position to do so. However, I do pretty much everything on my car for those exact reasons. It's not that I necessarily think I can do a better job than a professional tech with a professional shop, but at least I know EXACTLY what kind of job I did! I heavily track my car, and that intimate knowlege of its mechanical condition is a big help.

 

Yea I change my oil in the shop myself. Go downstairs drain it and change the filer myself. And add the oil myself. It's really fast see'ing how they have all the tools there I need.