I am not a big fan of pre-shave oils. Have tried several - Art of Shaving, Lloyd's, Proraso, olive oil, etc.
They look like they are raising the whiskers and they leave the skin softer, but always seem to significantly degrade the closeness of the shave.

Someone recently posted a saponification table from a very informative website: Saponification Table and Characteristics of Oils in Soap. I noted that the only oil that scored high for fluffy/stable lather and skin care was castor oil.
Although this information is about oil as a soap component, I decided to try castor oil as a pre-shave. Paid $3 for a 4 oz bottle in the drug store.

The castor oil was clear, odorless, and very, very stiff - kind of like mineral oil that has been in the freezer.
Did not seem to affect lathering with a variety of shave soaps/creams one way or the other - no better or worse.
Did seem to provide lubrication and left the skin softer. Did not irritate the skin.
Did not seem to degrade the closeness of the shave.
So, thinks this works as well - or a little better - than the other oils I have tried - just not sure I want to try to explain this to a non-straighter.

PS - the soap site was so kind as to send a link to their shaving soap recipe - Shaving Soap Recipe - How to Make Shaving Soap