I'm not running RSO. I remember in 0.16x I could see oil patches in the preview window. Getting back into the game on latest as of this post and I don't see any in the preview. Does that mean I won't have oil patches in game or does the mod add them as I explore?

See (almost at the bottom of) the Information tab:

Known limitations

    Deep sea oil does not show on the "generate preview" screen when starting a new game

Just explore the map and you should find lots of off-shore oil! Actually, there used to be so many patches that I turned down the frequency (under Modsettings --> Map) from "Normal" to "Very low". However, I didn't see any oil patches yet while walking along the coast line, so perhaps I'll have to change that to "Low" again. :-)

Awesome! And thanks for responding so quickly!