I was told by my chem teacher that oil and water are immiscible because water was polar and oil was non-polar, so that water molecules were attracted to each other, and forced the oil molecules up between the gaps. This is the "like dissolves like" rule of thumb.

 

However, in Skylab, it was discovered that ordinarily immiscible substances became miscible in microgravity. How does this fact relate to the one above?

no, they still don`t Mix/dissolve in the true sense of the word, you get something akin to an emullsion.

the polar/non polar thing still applies, however the means of seperation doesn`t in a micro-grav situation.

 

Oil is Lighter than water and so in a grav situation it will try to float and thus seperate.

where there is no grav, this means is taken away, and it doesn`t apply.

spin it in a centrifuge and it will though

There was a paper out a year or two ago saying that it relied on dissolved gases, and when gases are removed from a mixture oil and water mixed. Maybe it was the lack of atmosphere rather than gravity in the Skylab experiments.

 

http://www.future.org.au/news_2005/april/oil.html

I'm not positive, but I think the expirement was run inside Skylab.

dissolved gasses could at best form an emulsion, the low g would take away the seperating mechanism.