On Apr 15, 3:01*pm, Jules Richardson
wrote:
I've got an electric sewer pump which uses an oil-filled motor - the
lower seal had a tiny leak which I fixed, but it could use a little
topping up before I use it in anger (the upper bearing's *just*
protruding above the oil surface, so it doesn't need much to cover it
again).

Now, I think that the correct stuff is termed dielectric oil (which I've
been unable to find locally) - but that this *might* be the same as
transformer oil? (I've not seen the latter locally either, but at least
it lets me broaden my search!)

I also saw TNP mention recently that big transformers are filled with
mineral oil; is that true? Mineral oil I can certainly get (and indeed I
have a bottle somewhere) - unless of course not all mineral oils are
created equal, and the consumer-grade stuff is a completely different
animal :-)

cheers

Jules

About twenty years ago many were filled with PCB, a carcinogen.
You can't use mineral oil but transformer oil should be OK.
The oil has to be compatible with the insulation on the windings.

The oil is there primarily to cool the windings, it carries the heat
to the water being pumped.