Is a wet-mount needed to use Immersion Oil?
When I prepare my slide to use immersion oil, do I really need to wet-mount the specimen? Can I do it with just the coverslip?


Ideally you shouldn't use either with immersion oil. You should match the mounting media index as closely as possible to the immersion oil index, otherwise you'll reduce the resolution and contrast of your image. See:

http://www.microbehunter.com/the-importance-of-mounting-medium-refractive-index/


  Using water for the wet-mount gives you a sort-of time limit. You have to do your work before the water evaporates else you get little rivers at x100.


There are lots of options for higher index mounting media that will also preserve your specimen at least as well as air.