It`s a serious point that bryan made about the purity of the diluants....always double check, then check again to be sure it`s definitely the correct thing you`re buying, and if you`re still not sure, ask.
There was a forum thread from a while back where someone either asked about, or actually bought some di-propylene glycol - which is not the right stuff, but an easy mistake to make if not paying too much attention.
After a bit of discussion & checking it all came out in the wash - but could have had some implications if it hadn`t been picked up on...
..and the quality grades as well of course that have to be taken into account.
it`s always worth double checking.