Perhaps you should first do some reading on the properties of transformer
oil
before making an arbitrary decision to use automotive grade oil in your
transformer. The old and venerable J&P Transformer Book has good
information on
this subject. Using the wrong oil may compromise your transformer - and
your
insurance if it bursts into flames.

Long url so watch line wrap.

http://books.google.com.au/books?id=...&hl=en#PPP1,M1



Hey that looks like a pretty handy book.

LOL as for insurance, if they saw the "transformer" in the first place,
they'd probably crap a brick sideways. I think the oil bursting into flames
is the least of my worries with this unarguably dangerous concoction. At any
rate it will never be used for more than a few tens of seconds at a time,
and only while closely supervised. What fun is life without a little risk of
being vaporized?