Is there a temporary dye I can add to my fuel to watch it travel through the fuel lines?

[kenbw2]

I'm setting up a bit of a twin tank system for veg oil cold starts in the morning.

I want to know how much fuel needs to go through the filter, pump etc in order to purge what's in there.

My idea is to add some dye to the diesel (not red, obviously), run it through and see when the dye comes out of the pump's return.

But god knows what dye is safe to run through the fuel system, and I wouldn't want it to stain things.

Does such a thing exist?

[myglaren]

This any help?

Fuel Dyes.

Lots of other advice using that as a search term.

[Subsonicnat]

{IF} This is for testing purposes Why Not use Red,,,[in 1Ltr bottle in the line obviously}.
You only want to know how long it runs before being switched off to clear the line..
Easier with small amount which can be measured over short periods,,,Not like its in the main tank is it???.

[kenbw2]

Yea I saw the fuel dyes wikpedia page, done a bit of research myself. I found some UV dyes as well which could work. The thing I'm up against is knowing if it's safe t chuck in. Obviously I'm not gonna trust the eBay sellers saying "yea it's totally fine".

As for why not red, I've heard it does stain things so don't want to be accused in future, as well as not wanting to discolour my clear fuel lines.