Bottle just says Mineral Oil U.S.P.: Odorless, 
tasteless, colorless.

I've seen mineral spirits used as thinner, but I 
haven't seen canisters of mineral oil in the 
paint thinner section at hardware stores.  I have 
accidently gotten some mineral oil on some paint 
before, but nothing happened.  I wiped it off 
with a cloth and the cloth didn't get any paint 
on it either.

It really does remove the pesky dirt/dust spots 
from a cel.  You really don't notice the clear 
residue that it leaves behind except on 
multilayer cels.  Since mineral oil is lipid 
based, a chemist should know to use soapy water 
to get rid of any traces of mineral oil residue 
left over.

Result is a clean, spotless cel.  I really wish I 
had a before and after shot of my Ryoko w/ dinner 
table cel.  The cel was just filthy (no wonder 
the thumbnail was so small when I bought it).  I 
probably just increased its value 2-3x by 
cleaning it.

Below is a cropped scan of the cel.  The very 
right side of the cel, though, still needs some 
work.  (Especially when compared to the curtain 
on the very left).  Just imagine the whole cel 
being like that before the cleaning.