In between using high maintenance, finicky inks, I like to fill my pen with an ink that is going to hopefully clean the pen and maybe add an ink with lubricating properties. In the olden days after using an ink like BSB, I would completely flush the pen and then fill it with vintage Skrip Red. I've heard that the vintage Skrip inks were high in detergents which may account for why it seemed to do such a nice job cleaning the pen. Alas, those pens have been lost to the joys of having office staff and teenagers. (Yes, I give them fountain pens). I don't know if the Skrip red had any lubricating properties (I doubt it).
So, here I am, staring at a Vac 700 that has had various purple inks since it was released (that's about 18 months?). I've flushed it between uses, and then filled it again with another dark obnoxious purple. The last purple, Nostaligic Impressions (I did review it), was troublesome, but I can't blame the staining on just the NI ink because this pen has been sitting with purple ink in it for a long time, and some of those parts just stay purple. I've already flushed it, used JBB pen flush, flushed more, and flushed with a weak ammonia solution. The pen runs clear.
Anyway, I don't really want to take it apart at this time, and I don't care about the purple stains (eventually they will fade, or I maybe someday I'll care), but for now, I'd like to put in an ink that it would "whistle while it works" - as in it would clean and lube the pen.