vegetable oil = brake fluid?

["Megan Elora Caverly" <meca@domain.elided>]

In addition to our Alfa's I have a 67 Lancia Fulvia Zagato that I
bought a little over a year ago.  Most bugs have been sorted out, but
I'm left with a very strange one that I'm hoping the accumulated
wisdom here can help with.  The PO had the car serviced by a very
old-worldly minded mechanic who used vegetable oil in place of
standard brake fluid.  Per the manual, and I guess once upon a time
practice, this is/was a legitimate substitution option!  I do not want
to perpetuate it however, so does anyone here have any pertinent
experience with changing a brake system over from vegetable oil to
proper brake fluid?  I need to replace my brake lines anyway, so
they'll be fresh, but I'm wondering about seals, MC, etc. TIA,

Megan Caverly

P.S.  This is not a jest - I truly have veg.oil in the system, it's
weird stuff, and I want it replaced without worrying about a system
failure.  Body bits for this car are pretty much unobtainium. 

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